yonghua chen - Academia.edu (original) (raw)

Papers by yonghua chen

The International Journal of Advanced Manufacturing Technology, 2012

Surface quality is a very important factor to be considered in determining part build orientation... more Surface quality is a very important factor to be considered in determining part build orientation in rapid prototyping (RP) processes. Previous research has shown that parts built with inclined planes or curved surfaces along the build orientation have large staircase effect, thus have higher surface roughness compared to parts built with only vertical surfaces. However, as layers are getting thinner in rapid prototyping processes, the opposite might be true. In this study, a number of experiments and measurements are conducted first. In a single machine setup, two cylinders are built, one along axial direction and the other along transverse direction using an Objet® machine. Measurements have shown that surface roughness of RP parts built along the transverse direction is better than those from the axial direction. Through analysis and observation, the authors can conclude that when layers are small enough, surface curvature or slope along the build orientation may no longer be a major concern for RP part surface quality. Instead, the authors have observed that on-the-layer contour layout may cause even more serious surface quality problem. In other words, surface quality is not only dependent on build orientation, but more on scanning orientation on layers.

Product physical properties such as stiffness and surface friction are difficult or even impossib... more Product physical properties such as stiffness and surface friction are difficult or even impossible to be perceived in today's computer-aided design (CAD) systems. In this research, a haptic interface is developed to customize product physical properties such as product textures and stiffness. Using the proposed system, a designer can perceive, for examples, the surface roughness of a handle, the stiffness of a toothbrush, and exam the trigger force of a push button, or even feel the vibration while an electronic razor is powered on as if he/she is operating a real product. If any of the above physical properties is not desirable by the designer (or customer), the designer can easily make changes until customized properties are perceived. Since these physical properties of a product, traditionally evaluated based on physical prototypes, can now be perceived and modified without any cost in a virtual environment by designers, the product development cycle can be shortened and the...

Computer-Aided Design and Applications

Defects of primitive models such as holes are not uncommon in the process of reconstructing a phy... more Defects of primitive models such as holes are not uncommon in the process of reconstructing a physical object model through an optical scanner. Most hole-filling methods are focused on repairing model automatically. However automatic technologies cannot give satisfactory results when dealing with complex holes because points on the hole boundaries are error prone and must be pre-processed before any automatic methods be applied. In order to provide a more intuitive and efficient tool for model reconstruction in reverse engineering (RE) a novel hole-filling system with haptic characteristic based on triangular mesh is implemented compared with traditional unnatural mouse-based computer interfaces that can not be used to edit point clouds intuitively. Smoothing and stitching operations based on haptics are proposed to modify error-prone hole boundaries and simplify complex holes. A sculpting operation based on loop subdivision is developed to allow a user to deform the surface in the multi-sided and multi-level polygonal domains. By employing both automatic and interactive methods for hole filling, this system is more efficient and robust. A primitive prototype system has been implemented and several examples are presented to demonstrate the effectiveness of this system.

Soft Robotics

Despite the increasing popularity of soft robotic research, the application of soft robots is hin... more Despite the increasing popularity of soft robotic research, the application of soft robots is hindered by their limited ability to change compliance and acquire force and position feedback. In this article, both the controllability of compliance and the acquisition of position feedback are achieved in soft robotic fingers in the novel design of a three-dimensional (3D)-printed multismart material substrate. The substrate is composed of shape memory polymer (SMP) and conductive elastomer thermoplastic polyurethane (TPU). The SMP material is utilized to modulate the finger stiffness through its elastic modulus change around glass transition temperature (Tg). The conductive TPU has two functions: one is to tune SMP temperature by producing Joule heat when electrical power is supplied and the other is to provide position feedback of the finger by utilizing the piezoresistive effect of the conductive TPU. Theoretical modeling of finger position feedback and stiffness modulation are conducted. The theoretical analysis has been experimentally validated by a prototype robotic finger built from the proposed concept.

Soft Robotics

Abstract This article presents the design principle and fabrication of a variable stiffness soft ... more Abstract This article presents the design principle and fabrication of a variable stiffness soft robotic gripper for adaptive grasping and robust holding. The proposed robotic gripper is based on a finger design that combines a fiber-reinforced soft actuator and a particle pack. The soft actuator is responsible for the bending motion of the finger, and the particle pack acts as a stiffness-changeable interface between the finger and the object. In the natural state, the particle pack is soft and adaptive to part geometry. It can rapidly stiffen (through vacuum) to resist external load or to freeze the currently bent contour of the finger. Experimental studies have shown that more than a 10-fold stiffness enhancement is achievable. Therefore, the proposed gripper is capable of handling objects with different shapes, weights, and rigidities, which have been a great challenge for robotic grasping. For more effective grasping, a grasping strategy is designed for the proposed soft gripper with simultaneous con...

Computer-Aided Design and Applications

Virtual surgical planning and training require high fidelity not only in visual modeling, but als... more Virtual surgical planning and training require high fidelity not only in visual modeling, but also in haptic modeling. As a fundamental and typical application of surgical simulation, virtual suturing deals with technical problems such as soft tissue modeling, collision detection, and force modeling. In this paper, a haptic system of virtual suture is developed for surgical training. A realistic tissue modeling method based on either MRI or CT images is proposed. Given a CT or MRI file, an STL file is constructed. The STL file is voxelized to generate a regular spatial lattice that provides the basis for constructing the mass-spring system (MSS). Surface textures are mapped to this MSS for better visual effect of human tissues. Haptic interaction between the tissue model and a haptic device is rendered on a piecewise linear stress-strain model. A prototype system based on the proposed method is implemented. When using this system, a user can feel the force change at different stage of the suturing process. A force bar recording and showing the changing force in the suturing process provides an intuitive way of force magnitude display.

Soft Robotics

In this article, we have proposed a novel robotic finger design principle aimed to address two ch... more In this article, we have proposed a novel robotic finger design principle aimed to address two challenges in soft pneumatic grippers-the controllability of the stiffness and the controllability of the bending position. The proposed finger design is composed of a 3D printed multimaterial substrate and a soft pneumatic actuator. The substrate has four polylactic acid (PLA) segments interlocked with three shape memory polymer (SMP) joints, inspired by bones and joints in human fingers. By controlling the thermal energy of an SMP joint, the stiffness of the joints is modulated due to the dramatic change in SMP elastic modulus around its glass transition temperature (Tg). When SMP joints are heated above Tg, they exhibit very small stiffness, allowing the finger to easily bend around the SMP joints if the attached soft actuator is actuated. When there is no force from the soft actuator, shape recovery stress in SMP contributes to the finger's shape restoration. Since each joint's rotation can be individually controlled, the position control of the finger is made possible. Experimental analysis has been conducted to show the finger's variable stiffness and the result is compared with the analytical values. It is found that the stiffness ratio can be 24.9 times for a joint at room temperature (20°C) and at an elevated temperature of 60°C when air pressure p of the soft actuator is turned off. Finally, a gripper composed of two fingers is fabricated for demonstration.

Computer-Aided Design and Applications, 2009

We present the Enhanced Anthropometric Rating System (EARS), an automated system for evaluating t... more We present the Enhanced Anthropometric Rating System (EARS), an automated system for evaluating the quality of 3D human body scans. EARS is able to detect and classify both the geometric and anthropometric features of a given mesh and rates its quality. These features and corresponding operations include the roughness of the scanned surface, the fairness of vertex location, area and position of missing body parts, anthropometrically guided segmentation, detection of landmarks, and wrinkles in clothing. The system ranks these features and operations based on their importance as determined by Anthropologists who have specific requirements with respect to understanding the anthropometry of the soldier of the 21 st century. The data scans contain more than 100,000 vertices and over 300,000 facets. The system is able to provide real-time feedback on whether the mesh is suitable for downstream applications. The system will be used by the U.S. Army to do statistical studies on their large human body dataset.

2009 IEEE International Conference on Virtual Environments, Human-Computer Interfaces and Measurements Systems, 2009

In this paper, a novel haptic rendering method based on artificial neural network is proposed for... more In this paper, a novel haptic rendering method based on artificial neural network is proposed for turning simulation. In the proposed method, a two-layer neural network structure with three inputs and one output is used to model the cutting force. Levenberg-Marquardt algorithm is exploited as a learning strategy for training the neural network based on experimental machining data. Using the trained neural network, the relationship between simulated cutting force and cutting conditions can be obtained. Based on this method, a haptic virtual machining operation system is implemented and presented in this paper.

Mechatronics, 2015

Abstract Highly flexible soft robotic arms are safe for human–machine interaction. Particle Jammi... more Abstract Highly flexible soft robotic arms are safe for human–machine interaction. Particle Jamming has been demonstrated to be very effective for soft robotic arms with stiffness modulation by pneumatic means. However, the structural uncertainty due to particle re-organization makes particle jamming based soft robotic arms unreliable in both position and stiffness control. Ball joint based robotic arms have good structural integrity and good positional control property. Yet their stiffness modulation is very difficult. Instead of modulating stiffness using wires, this research proposes stiffness modulation of ball joint based robotic spines using vacuum energy. To strengthen the spine arm stiffness, particles are integrated into the ball joint spine. Both analysis and experimental studies in this research have shown that the integrated robotic spine has much better performance in terms of stiffness compared to the ball joint based spine without particle jamming. In fact, experimental studies have shown stiffness enhancement of 13 times. The proposed soft robotic spine can be used in applications where a large band of stiffness modulation is required.

Computer-Aided Design and Applications, 2010

Parts built from rapid prototyping processes have heterogeneous properties in both geometric form... more Parts built from rapid prototyping processes have heterogeneous properties in both geometric form and mechanical strength. Build orientation is one of the key factors that determine how such properties are distributed in the parts. In previous studies, the selection of build orientations for the shortest build time, the best part accuracy has been reported. This study aims to investigate how to determine the build orientation so that a part built in the orientation can be subjected to the same load with the minimum deformation or strain. In the research, the selective laser sintering (SLS) technique has been used to make the test specimens. The relationships between stress/strain against build orientations are obtained through tensile test experiments. Such relationships are modeled as mathematic equations which are used for the selection of the best build orientation so that parts built in such orientation will have minimum tensile strain when subjected to the same load pattern.

2008 IEEE International Conference on Robotics and Biomimetics, 2009

When doing femur fracture reduction surgery, both patient and surgeon are exposed to a great amou... more When doing femur fracture reduction surgery, both patient and surgeon are exposed to a great amount of radiation, which is harmful to their health. Computer assisted orthopaedic surgery (CAOS) is a less invasive approach for its ability to reduce the usage of image intensifier. Various robots have been developed for femur fracture reduction surgery. Most of these robots are beared

2014 10th International Conference on Natural Computation (ICNC), 2014

Swarm intelligence (SI), inspired by collective behavior of animals, has drawn much attention for... more Swarm intelligence (SI), inspired by collective behavior of animals, has drawn much attention for its advantages in solving complex engineering problems. There are currently various forms of algorithms derived from mimicking swarm behavior. A key component of such algorithms is the determination of how each individual in a population behaves. In this paper, the evolution of a population is determined by a novel decision-making model that combines the effect of Leadership, Optimal foraging and Threshold response (LOT) which is expressed as simple mathematical formulas. Based on these formulas, rules governing the decision-making process of each individual in a population are formulated. In order to verify the effectiveness of the proposed LOT decision-making model, five highly multi-modal functions of varying difficulties are tested together with the Particle Swarm Optimization (PSO) method. The LOT model has shown excellent performance in accuracy and global search ability compared with PSO.

Advanced Robotics, 2014

The modern society is fuelled by very comprehensive grids of gas and liquid pipelines. In recent ... more The modern society is fuelled by very comprehensive grids of gas and liquid pipelines. In recent years, various in-pipe robots have been developed for inspection and maintenance tasks inside such pipes. In this paper, a novel in-pipe robot is proposed and developed for gas/oil well interventions at thousands of meters downhole. Due to the nature of such intervention, in-pipe robot design must be capable of carrying a very large payload, as large as 2500 N inside a pipe with diameter as small as 54 mm. The proposed design concept is based on a compound planetary gearing system. One of the major novelties of this design is the use of pipe wall as a ring gear for one stage of the compound planetary gear system; the other novelty is the generation of helical angle when the planetary gears are expanded to press on the pipe wall. The proposed concept is compact, efficient, and has never been reported before. In this paper, the helical angle, the velocity, and load capability of the proposed system will be analyzed. The load transportation capability of the proposed robot is also measured based on an experiment. Initial data have shown great potential in carrying large payloads. Graphical Abstract

2011 4th International Conference on Biomedical Engineering and Informatics (BMEI), 2011

Steerable needles are widely used in minimally invasive surgery. To perform medical tasks well in... more Steerable needles are widely used in minimally invasive surgery. To perform medical tasks well in the deep of a human body, it is required that a needle is easier and more accurate to be controlled and steered. In this paper, the thrusting performances of a one-direction bendable needle are investigated in detail. Such a needle consists of a bevel-tip head,

2010 3rd International Conference on Biomedical Engineering and Informatics, 2010

... Yong Hu Department of Orthopaedics and Traumatology The University of Hong Kong HongKong SAR,... more ... Yong Hu Department of Orthopaedics and Traumatology The University of Hong Kong HongKong SAR, PR China ... After the head is bent an angle I β , as shown in Fig. 9, the thrusting force I F can be divided a force Ib F and a force It F on the first articulation: sin cos Ib I I It I I F F ...

Computer-Aided Design and Applications, 2008

Needle based surgery is an important surgical technique for its minimally invasive interventions.... more Needle based surgery is an important surgical technique for its minimally invasive interventions. The insertion of a long and slender needle into the complicated human body is a very challenging procedure. In this paper, a compliant needle is designed to facilitate the obstacle avoidance and path control that are inevitable in some surgical operations. During needle insertion, a magnetic force is employed to steer the compliant needle when needed. The steerable needle insertion process is simulated in a haptic system which can provide users both visual and haptic feedback.

Computer-Aided Design and Applications, 2004

Ribbons may be used for the modeling of DNAs and proteins. The topology of a ribbon can be descri... more Ribbons may be used for the modeling of DNAs and proteins. The topology of a ribbon can be described by the link Lk, while its geometry is represented by the writhe Wr and the twist Tw. These three quantities are numerical integrals and are related by a single formula from knot theory. This article discusses the meanings of these three quantities, offers an approach for calculating their numerical values, and provides some examples.

Computer-Aided Design and Applications, 2005

An inspection path generation methodology for virtual coordinate measuring machines (VCMM) based ... more An inspection path generation methodology for virtual coordinate measuring machines (VCMM) based on haptic technologies is presented in this paper. Introducing a haptic device into CMM inspection path planning leads to the development of the proposed novel CMM off-line inspection path planning environment called haptic virtual CMM (HVCMM). HVCMM is an accurate model of a real CMM, which simulates a CMM's operation and its measurement process in a virtual environment with haptic perception. Due to the force feed back in the operation, the inspection path planning process is more intuitive, efficient, and user-friendly. The inspection path generation procedure is carried out in several steps: first, the measuring points are selected by operators using "point-and-click" method; second, the measuring points are offset according to the surface geometry and the offset points are linked with line segments; third, the linked path is traced by the virtual CMM probe to perform collision detection; fourth, when a collision occurred, an auxiliary point method and a teach pendant method are developed to generate a collision-free path with the aid of haptic constraint plane. The aim of these algorithms is to minimize the computation of collision detection. Examples are given on a HVCMM prototype system to demonstrate the proposed methodology.

2007 IEEE International Conference on Robotics and Biomimetics (ROBIO), 2007

Page 1. Magnetic Force Aided Compliant Needle Navigation and Needle Performance Analysis * Libo T... more Page 1. Magnetic Force Aided Compliant Needle Navigation and Needle Performance Analysis * Libo Tang, Yonghua Chen and Xuejian He Department of Mechanical Engineering The University of Hong Kong Pokfulam Road, Hong Kong, China yhchen@hku.hk ...

The International Journal of Advanced Manufacturing Technology, 2012

Surface quality is a very important factor to be considered in determining part build orientation... more Surface quality is a very important factor to be considered in determining part build orientation in rapid prototyping (RP) processes. Previous research has shown that parts built with inclined planes or curved surfaces along the build orientation have large staircase effect, thus have higher surface roughness compared to parts built with only vertical surfaces. However, as layers are getting thinner in rapid prototyping processes, the opposite might be true. In this study, a number of experiments and measurements are conducted first. In a single machine setup, two cylinders are built, one along axial direction and the other along transverse direction using an Objet® machine. Measurements have shown that surface roughness of RP parts built along the transverse direction is better than those from the axial direction. Through analysis and observation, the authors can conclude that when layers are small enough, surface curvature or slope along the build orientation may no longer be a major concern for RP part surface quality. Instead, the authors have observed that on-the-layer contour layout may cause even more serious surface quality problem. In other words, surface quality is not only dependent on build orientation, but more on scanning orientation on layers.

Product physical properties such as stiffness and surface friction are difficult or even impossib... more Product physical properties such as stiffness and surface friction are difficult or even impossible to be perceived in today's computer-aided design (CAD) systems. In this research, a haptic interface is developed to customize product physical properties such as product textures and stiffness. Using the proposed system, a designer can perceive, for examples, the surface roughness of a handle, the stiffness of a toothbrush, and exam the trigger force of a push button, or even feel the vibration while an electronic razor is powered on as if he/she is operating a real product. If any of the above physical properties is not desirable by the designer (or customer), the designer can easily make changes until customized properties are perceived. Since these physical properties of a product, traditionally evaluated based on physical prototypes, can now be perceived and modified without any cost in a virtual environment by designers, the product development cycle can be shortened and the...

Computer-Aided Design and Applications

Defects of primitive models such as holes are not uncommon in the process of reconstructing a phy... more Defects of primitive models such as holes are not uncommon in the process of reconstructing a physical object model through an optical scanner. Most hole-filling methods are focused on repairing model automatically. However automatic technologies cannot give satisfactory results when dealing with complex holes because points on the hole boundaries are error prone and must be pre-processed before any automatic methods be applied. In order to provide a more intuitive and efficient tool for model reconstruction in reverse engineering (RE) a novel hole-filling system with haptic characteristic based on triangular mesh is implemented compared with traditional unnatural mouse-based computer interfaces that can not be used to edit point clouds intuitively. Smoothing and stitching operations based on haptics are proposed to modify error-prone hole boundaries and simplify complex holes. A sculpting operation based on loop subdivision is developed to allow a user to deform the surface in the multi-sided and multi-level polygonal domains. By employing both automatic and interactive methods for hole filling, this system is more efficient and robust. A primitive prototype system has been implemented and several examples are presented to demonstrate the effectiveness of this system.

Soft Robotics

Despite the increasing popularity of soft robotic research, the application of soft robots is hin... more Despite the increasing popularity of soft robotic research, the application of soft robots is hindered by their limited ability to change compliance and acquire force and position feedback. In this article, both the controllability of compliance and the acquisition of position feedback are achieved in soft robotic fingers in the novel design of a three-dimensional (3D)-printed multismart material substrate. The substrate is composed of shape memory polymer (SMP) and conductive elastomer thermoplastic polyurethane (TPU). The SMP material is utilized to modulate the finger stiffness through its elastic modulus change around glass transition temperature (Tg). The conductive TPU has two functions: one is to tune SMP temperature by producing Joule heat when electrical power is supplied and the other is to provide position feedback of the finger by utilizing the piezoresistive effect of the conductive TPU. Theoretical modeling of finger position feedback and stiffness modulation are conducted. The theoretical analysis has been experimentally validated by a prototype robotic finger built from the proposed concept.

Soft Robotics

Abstract This article presents the design principle and fabrication of a variable stiffness soft ... more Abstract This article presents the design principle and fabrication of a variable stiffness soft robotic gripper for adaptive grasping and robust holding. The proposed robotic gripper is based on a finger design that combines a fiber-reinforced soft actuator and a particle pack. The soft actuator is responsible for the bending motion of the finger, and the particle pack acts as a stiffness-changeable interface between the finger and the object. In the natural state, the particle pack is soft and adaptive to part geometry. It can rapidly stiffen (through vacuum) to resist external load or to freeze the currently bent contour of the finger. Experimental studies have shown that more than a 10-fold stiffness enhancement is achievable. Therefore, the proposed gripper is capable of handling objects with different shapes, weights, and rigidities, which have been a great challenge for robotic grasping. For more effective grasping, a grasping strategy is designed for the proposed soft gripper with simultaneous con...

Computer-Aided Design and Applications

Virtual surgical planning and training require high fidelity not only in visual modeling, but als... more Virtual surgical planning and training require high fidelity not only in visual modeling, but also in haptic modeling. As a fundamental and typical application of surgical simulation, virtual suturing deals with technical problems such as soft tissue modeling, collision detection, and force modeling. In this paper, a haptic system of virtual suture is developed for surgical training. A realistic tissue modeling method based on either MRI or CT images is proposed. Given a CT or MRI file, an STL file is constructed. The STL file is voxelized to generate a regular spatial lattice that provides the basis for constructing the mass-spring system (MSS). Surface textures are mapped to this MSS for better visual effect of human tissues. Haptic interaction between the tissue model and a haptic device is rendered on a piecewise linear stress-strain model. A prototype system based on the proposed method is implemented. When using this system, a user can feel the force change at different stage of the suturing process. A force bar recording and showing the changing force in the suturing process provides an intuitive way of force magnitude display.

Soft Robotics

In this article, we have proposed a novel robotic finger design principle aimed to address two ch... more In this article, we have proposed a novel robotic finger design principle aimed to address two challenges in soft pneumatic grippers-the controllability of the stiffness and the controllability of the bending position. The proposed finger design is composed of a 3D printed multimaterial substrate and a soft pneumatic actuator. The substrate has four polylactic acid (PLA) segments interlocked with three shape memory polymer (SMP) joints, inspired by bones and joints in human fingers. By controlling the thermal energy of an SMP joint, the stiffness of the joints is modulated due to the dramatic change in SMP elastic modulus around its glass transition temperature (Tg). When SMP joints are heated above Tg, they exhibit very small stiffness, allowing the finger to easily bend around the SMP joints if the attached soft actuator is actuated. When there is no force from the soft actuator, shape recovery stress in SMP contributes to the finger's shape restoration. Since each joint's rotation can be individually controlled, the position control of the finger is made possible. Experimental analysis has been conducted to show the finger's variable stiffness and the result is compared with the analytical values. It is found that the stiffness ratio can be 24.9 times for a joint at room temperature (20°C) and at an elevated temperature of 60°C when air pressure p of the soft actuator is turned off. Finally, a gripper composed of two fingers is fabricated for demonstration.

Computer-Aided Design and Applications, 2009

We present the Enhanced Anthropometric Rating System (EARS), an automated system for evaluating t... more We present the Enhanced Anthropometric Rating System (EARS), an automated system for evaluating the quality of 3D human body scans. EARS is able to detect and classify both the geometric and anthropometric features of a given mesh and rates its quality. These features and corresponding operations include the roughness of the scanned surface, the fairness of vertex location, area and position of missing body parts, anthropometrically guided segmentation, detection of landmarks, and wrinkles in clothing. The system ranks these features and operations based on their importance as determined by Anthropologists who have specific requirements with respect to understanding the anthropometry of the soldier of the 21 st century. The data scans contain more than 100,000 vertices and over 300,000 facets. The system is able to provide real-time feedback on whether the mesh is suitable for downstream applications. The system will be used by the U.S. Army to do statistical studies on their large human body dataset.

2009 IEEE International Conference on Virtual Environments, Human-Computer Interfaces and Measurements Systems, 2009

In this paper, a novel haptic rendering method based on artificial neural network is proposed for... more In this paper, a novel haptic rendering method based on artificial neural network is proposed for turning simulation. In the proposed method, a two-layer neural network structure with three inputs and one output is used to model the cutting force. Levenberg-Marquardt algorithm is exploited as a learning strategy for training the neural network based on experimental machining data. Using the trained neural network, the relationship between simulated cutting force and cutting conditions can be obtained. Based on this method, a haptic virtual machining operation system is implemented and presented in this paper.

Mechatronics, 2015

Abstract Highly flexible soft robotic arms are safe for human–machine interaction. Particle Jammi... more Abstract Highly flexible soft robotic arms are safe for human–machine interaction. Particle Jamming has been demonstrated to be very effective for soft robotic arms with stiffness modulation by pneumatic means. However, the structural uncertainty due to particle re-organization makes particle jamming based soft robotic arms unreliable in both position and stiffness control. Ball joint based robotic arms have good structural integrity and good positional control property. Yet their stiffness modulation is very difficult. Instead of modulating stiffness using wires, this research proposes stiffness modulation of ball joint based robotic spines using vacuum energy. To strengthen the spine arm stiffness, particles are integrated into the ball joint spine. Both analysis and experimental studies in this research have shown that the integrated robotic spine has much better performance in terms of stiffness compared to the ball joint based spine without particle jamming. In fact, experimental studies have shown stiffness enhancement of 13 times. The proposed soft robotic spine can be used in applications where a large band of stiffness modulation is required.

Computer-Aided Design and Applications, 2010

Parts built from rapid prototyping processes have heterogeneous properties in both geometric form... more Parts built from rapid prototyping processes have heterogeneous properties in both geometric form and mechanical strength. Build orientation is one of the key factors that determine how such properties are distributed in the parts. In previous studies, the selection of build orientations for the shortest build time, the best part accuracy has been reported. This study aims to investigate how to determine the build orientation so that a part built in the orientation can be subjected to the same load with the minimum deformation or strain. In the research, the selective laser sintering (SLS) technique has been used to make the test specimens. The relationships between stress/strain against build orientations are obtained through tensile test experiments. Such relationships are modeled as mathematic equations which are used for the selection of the best build orientation so that parts built in such orientation will have minimum tensile strain when subjected to the same load pattern.

2008 IEEE International Conference on Robotics and Biomimetics, 2009

When doing femur fracture reduction surgery, both patient and surgeon are exposed to a great amou... more When doing femur fracture reduction surgery, both patient and surgeon are exposed to a great amount of radiation, which is harmful to their health. Computer assisted orthopaedic surgery (CAOS) is a less invasive approach for its ability to reduce the usage of image intensifier. Various robots have been developed for femur fracture reduction surgery. Most of these robots are beared

2014 10th International Conference on Natural Computation (ICNC), 2014

Swarm intelligence (SI), inspired by collective behavior of animals, has drawn much attention for... more Swarm intelligence (SI), inspired by collective behavior of animals, has drawn much attention for its advantages in solving complex engineering problems. There are currently various forms of algorithms derived from mimicking swarm behavior. A key component of such algorithms is the determination of how each individual in a population behaves. In this paper, the evolution of a population is determined by a novel decision-making model that combines the effect of Leadership, Optimal foraging and Threshold response (LOT) which is expressed as simple mathematical formulas. Based on these formulas, rules governing the decision-making process of each individual in a population are formulated. In order to verify the effectiveness of the proposed LOT decision-making model, five highly multi-modal functions of varying difficulties are tested together with the Particle Swarm Optimization (PSO) method. The LOT model has shown excellent performance in accuracy and global search ability compared with PSO.

Advanced Robotics, 2014

The modern society is fuelled by very comprehensive grids of gas and liquid pipelines. In recent ... more The modern society is fuelled by very comprehensive grids of gas and liquid pipelines. In recent years, various in-pipe robots have been developed for inspection and maintenance tasks inside such pipes. In this paper, a novel in-pipe robot is proposed and developed for gas/oil well interventions at thousands of meters downhole. Due to the nature of such intervention, in-pipe robot design must be capable of carrying a very large payload, as large as 2500 N inside a pipe with diameter as small as 54 mm. The proposed design concept is based on a compound planetary gearing system. One of the major novelties of this design is the use of pipe wall as a ring gear for one stage of the compound planetary gear system; the other novelty is the generation of helical angle when the planetary gears are expanded to press on the pipe wall. The proposed concept is compact, efficient, and has never been reported before. In this paper, the helical angle, the velocity, and load capability of the proposed system will be analyzed. The load transportation capability of the proposed robot is also measured based on an experiment. Initial data have shown great potential in carrying large payloads. Graphical Abstract

2011 4th International Conference on Biomedical Engineering and Informatics (BMEI), 2011

Steerable needles are widely used in minimally invasive surgery. To perform medical tasks well in... more Steerable needles are widely used in minimally invasive surgery. To perform medical tasks well in the deep of a human body, it is required that a needle is easier and more accurate to be controlled and steered. In this paper, the thrusting performances of a one-direction bendable needle are investigated in detail. Such a needle consists of a bevel-tip head,

2010 3rd International Conference on Biomedical Engineering and Informatics, 2010

... Yong Hu Department of Orthopaedics and Traumatology The University of Hong Kong HongKong SAR,... more ... Yong Hu Department of Orthopaedics and Traumatology The University of Hong Kong HongKong SAR, PR China ... After the head is bent an angle I β , as shown in Fig. 9, the thrusting force I F can be divided a force Ib F and a force It F on the first articulation: sin cos Ib I I It I I F F ...

Computer-Aided Design and Applications, 2008

Needle based surgery is an important surgical technique for its minimally invasive interventions.... more Needle based surgery is an important surgical technique for its minimally invasive interventions. The insertion of a long and slender needle into the complicated human body is a very challenging procedure. In this paper, a compliant needle is designed to facilitate the obstacle avoidance and path control that are inevitable in some surgical operations. During needle insertion, a magnetic force is employed to steer the compliant needle when needed. The steerable needle insertion process is simulated in a haptic system which can provide users both visual and haptic feedback.

Computer-Aided Design and Applications, 2004

Ribbons may be used for the modeling of DNAs and proteins. The topology of a ribbon can be descri... more Ribbons may be used for the modeling of DNAs and proteins. The topology of a ribbon can be described by the link Lk, while its geometry is represented by the writhe Wr and the twist Tw. These three quantities are numerical integrals and are related by a single formula from knot theory. This article discusses the meanings of these three quantities, offers an approach for calculating their numerical values, and provides some examples.

Computer-Aided Design and Applications, 2005

An inspection path generation methodology for virtual coordinate measuring machines (VCMM) based ... more An inspection path generation methodology for virtual coordinate measuring machines (VCMM) based on haptic technologies is presented in this paper. Introducing a haptic device into CMM inspection path planning leads to the development of the proposed novel CMM off-line inspection path planning environment called haptic virtual CMM (HVCMM). HVCMM is an accurate model of a real CMM, which simulates a CMM's operation and its measurement process in a virtual environment with haptic perception. Due to the force feed back in the operation, the inspection path planning process is more intuitive, efficient, and user-friendly. The inspection path generation procedure is carried out in several steps: first, the measuring points are selected by operators using "point-and-click" method; second, the measuring points are offset according to the surface geometry and the offset points are linked with line segments; third, the linked path is traced by the virtual CMM probe to perform collision detection; fourth, when a collision occurred, an auxiliary point method and a teach pendant method are developed to generate a collision-free path with the aid of haptic constraint plane. The aim of these algorithms is to minimize the computation of collision detection. Examples are given on a HVCMM prototype system to demonstrate the proposed methodology.

2007 IEEE International Conference on Robotics and Biomimetics (ROBIO), 2007

Page 1. Magnetic Force Aided Compliant Needle Navigation and Needle Performance Analysis * Libo T... more Page 1. Magnetic Force Aided Compliant Needle Navigation and Needle Performance Analysis * Libo Tang, Yonghua Chen and Xuejian He Department of Mechanical Engineering The University of Hong Kong Pokfulam Road, Hong Kong, China yhchen@hku.hk ...