Bin Yao | Purdue University (original) (raw)

Papers by Bin Yao

Dynamic Systems and Control, 2002

In the fall of 2001 we implemented a new controller design project in our Junior/Senior level con... more In the fall of 2001 we implemented a new controller design project in our Junior/Senior level controls class in Mechanical Engineering at Purdue University. The old project, which involved the identification and control of a “black box”, failed to challenge and motivate students. Our new project is the design of a controller for the point-to-point motion of a gantry crane system. Student teams modeled the gantry crane and developed a controller to meet several performance specifications. The designs were implemented in Simulink with MATLAB’s Real-Time Workshop. A competition served to further motivate the students. In the end we were very impressed with the great effort the students gave and the quality of their designs. Each group presented their design and most students stayed and asked questions for several hours.

2007 IEEE/ASME international conference on advanced intelligent mechatronics, 2007

This paper presents the problem of fault detection in the presence of input unmodeled dynamics. T... more This paper presents the problem of fault detection in the presence of input unmodeled dynamics. There are mainly two sources of uncertainties for a system in addition to external disturbances: parametric uncertainties and unmodeled dynamics. For nonlinear systems, the problem of fault detection and isolation has been studied under the assumption that modeling uncertainty can be bounded by an a priori known function. Many robust algorithms have been designed based on this assumption. But, the problem of fault detection in the presence of dynamic uncertainties for nonlinear systems has not been addressed by many researchers. The goal of this work is to focus on the problem of actuator fault detection in the presence of input unmodeled dynamics. We use stateestimation errors as residuals for fault detection and monitoring the system for any off-nominal behavior. A rigorous analysis is done to understand the effects of unmodeled dynamics on the process of fault detection. Based on the analysis, we derive a threshold function for the purpose of fault detection, which can decouple the effects of fault and unmodeled dynamics. Finally, simulations are performed to show the effectiveness of the proposed method.

Dynamic Systems and Control, Parts A and B, 2006

The combined use of Variable Geometry Turbine (VGT) and Exhaust Gas Recirculation (EGR) gives us ... more The combined use of Variable Geometry Turbine (VGT) and Exhaust Gas Recirculation (EGR) gives us an opportunity to reduce emissions, without compromising the need to generate more power. In the present work, a multivariable approach is used to tackle the EGR-VGT actuator control problem. A linear multivariable controller is designed using Lyapunov's Indirect Method, based on the Jacobian matrix of the system. Then, some stronger conditions are sought to be satisfied by the Jacobian matrix, which would ensure the Global Asymptotic Stability of the system. These conditions are derived using Nonlinear Contraction Analysis. Finally, simulations are performed on a simplified model with three states to evaluate the performance of the controllers.

2010 11th IEEE International Workshop on Advanced Motion Control (AMC), 2010

The ever increasingly stringent performance requirements of modern mechanical systems have forced... more The ever increasingly stringent performance requirements of modern mechanical systems have forced control engineers to look beyond traditional linear control theory for more advanced nonlinear controllers. During the past decade, a mathematically rigorous nonlinear adaptive robust control (ARC) theory has been developed and has been experimentally demonstrated achieving significant performance improvement in a number of motion control applications. This plenary paper first uses a simple motion control problem as an example to bring out the conceptual connection and nonlinear extension of the widely used PID controller structure to the developed ARC approach. Through this example, some of the key underlying working mechanisms of the ARC theory can be grasped easily. The paper then highlights how major issues in the precision motion control can be handled systematically and effectively with the ARC framework. The issues considered include (i) large variations of physical parameters of a system; (ii) unknown nonlinearities such as cogging and ripple forces of linear motors; (iii) dynamic uncertain nonlinearities with non-uniformly detectable unmeasured internal states (e.g., friction described by dynamic models in high precision motion controls); and (iv) control input saturation due to limited capacity of physical actuators. The precision motion control of a linear motor driven high-speed/high-acceleration industrial gantry is used as a case study and comparative experimental results are presented to illustrate the achievable performance and limitations of various ARC controllers in implementation.

IEEE/ASME Transactions on Mechatronics, 2000

High performance robust motion control of single-rod hydraulic actuators is considered. In contra... more High performance robust motion control of single-rod hydraulic actuators is considered. In contrast t o the double-rod hydraulic actuators studied previously, the two chambers of a single-rod hydraulic actuator have different areas. As a result, the dynamic equations describing the pressure changes in the two chambers cannot be combined into a single load pressure equation. This complicates the controller design since it not only increases the dimension of the system to be dealt with but also brings in the stability issue of the added internal dynamics. A discontinuous projection based adaptive robust controller is constructed. The controller is able to take into account not only the effect of parameter variations coming from the inertia load and various hydraulic parameters but also the effect of hardto-model nonlinearities such as uncompensated friction forces and external disturbances. Extensive experimental results are obtained for the swing motion control of a hydraulic arm. I n comparison to a state-of-the-art industrial motion controller, the proposed ARC algorithm achieves more than a magnitude reduction of tracking errors. Furthermore, during constant velocity and regulation periods, the ARC controller reduces the tracking errors almost down to the measurement resolution level.

Many robotic systems, like surgical robots, robotic hands, and exoskeleton robots, use cable pass... more Many robotic systems, like surgical robots, robotic hands, and exoskeleton robots, use cable passing through conduits to actuate remote instruments. Cable actuation simplifies the design and allows the actuator to be located at a convenient location, away from the end effector. However, nonlinear frictions between the cable and the conduit account for major losses in tension transmission across the cable, and a model is needed to characterize their effects in order to analyze and compensate for them. Although some models have been proposed in the literature, they are lumped parameter based and restricted to the very special case of a single cable with constant conduit curvature and constant pretension across the cable only. This paper proposes a mathematically rigorous distributed parameter model for cable-conduit actuation with any curvature and initial tension profile across the cable. The model, which is described by a set of partial differential equations in the continuous time-domain, is also discretized for the effective numerical simulation of the cable motion and tension transmission across the cable. Unlike the existing lumped-parameter-based models, the resultant discretized model enables one to accurately simulate the partial-moving/partial-sticking cable motion of the cable-conduit actuation with any curvature and initial tension profile. The model is further extended to cable-conduit actuation in pull-pull configuration using a pair of cables. Various simulations results are presented to reveal the unique phenomena like backlash, cable slacking, interaction between the two cables, and other nonlinear behaviors associated with the cable conduits in pullpull configuration. These results are verified by experiments using two dc motors coupled with a cable-conduit pair. The experimental setup has been prepared to emulate a typical cable-actuated robotic system. Experimental results are compared with the simulations and various implications are discussed.

2008 IEEE International Conference on Robotics and Automation, 2008

Many surgical robots use cable-conduit pairs in a pull-pull configuration to actuate the instrume... more Many surgical robots use cable-conduit pairs in a pull-pull configuration to actuate the instruments and transmit power into the patient's body. Friction between the cable and the conduit makes the system nonlinear and accounts for major losses in tension transmission across the cable. This paper proposes an analytical model for a similar cable-conduit system and formulates the load transmission characteristics. The dynamic model uses discrete elements with friction losses and cable stretch calculated for each of the segments. The simulations predict backlash, cable slacking, and other nonlinear behavior. These results are verified with an experiment using two DC motors coupled with a cable-conduit pair. The drive motor is run in position control mode, while the load motor simulates a passive environment torsional spring. Experimental results are compared with the simulation and various implications are discussed.

Adaptive motion and force control of manipulators in constrained motion in the presence of parame... more Adaptive motion and force control of manipulators in constrained motion in the presence of parametric uncertainties both in the robot and contact surfaces is solved in this paper. A new constrained dynamic model is obtained to account for the effect of contact surface friction. An adaptive law is suggested with unknown parameters updated by both motion and force tracking errors

Dynamic Systems and Control, Parts A and B, 2005

This paper presented multi-objective optimization of tip tracking control for non-collocated flex... more This paper presented multi-objective optimization of tip tracking control for non-collocated flexible beam. The desired trajectory is specified at the tip displacement of the flexible struc- ture, which undergoes translation base motion actuated by a lin- ear motor. The system model is first formulated from modal truncation approach for the flexible structure representing a sin- gle Cartesian robot manipulator. The linear system model of the flexible structure always has structural uncertainties. Robust sta- bility and robust performance on tip tracking can be expressed as H2/H∞ norm constraints, which are converted into the Linear Matrix Inequality (LMI). The multi-objective controller design is solved by the convex minimization. In order to reduce the con- servatism generated when the same Lyapunov matrix is selected, the Lyapunov matrix is scaled for different norm constraints. Simulation results have demonstrated favorable tip tracking of the proposed robust controller.

Dynamic Systems and Control, Parts A and B, 2006

2006 American Control Conference, 2006

ABSTRACT The back-stepping designs based on confine functions are suggested for the robust output... more ABSTRACT The back-stepping designs based on confine functions are suggested for the robust output-feedback global stabilization of a class of nonlinear continuous systems; the proposed stabilizer is efficient for the nonlinear continuous systems confined by a bound function, the nonlinearities of the systems may be of varied forms or uncertain; the designed stabilizer is robust means that a class of nonlinear continuous systems can be stabilized by the same output feedback stabilization schemes: numerical simulation examples are given.

2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2010

This paper proposes a sensorless force estimation method for the end effector tip of a surgical r... more This paper proposes a sensorless force estimation method for the end effector tip of a surgical robot instrument. Due to various size and safety constraints related to the surgical robot instrument, it is difficult to measure the reaction force at the instrument tip. This paper presents a method of estimating the reaction force of the surgical robot instrument without sensors and attempts to use state observer of control algorithm. Sliding mode control with sliding perturbation observer (SMCSPO) is used to drive the instrument, where the sliding perturbation observer (SPO) computes the amount of perturbation defined as the combination of the uncertainties and nonlinear terms where the major uncertainties arise from the reaction force. Based on this idea, this paper proposes a method to estimate the reaction force on the end-effector tip of the surgical robot instruments using only SPO and encoder without any additional sensors. To evaluate the validity of this paper, experiment was performed and the results showed that the estimated force computed from SPO is similar to the actual force.

2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2010

Linear electrical loading system (LELS) driven by electrical cylinder with permanent magnet synch... more Linear electrical loading system (LELS) driven by electrical cylinder with permanent magnet synchronous motor (PMSM) offers several advantages of high transmission efficiency and high precision positioning, however these advantages are obtained at the expense of larger friction in mechanism and added difficulties in controlling such a force servo system. To address the problems, the LuGre friction model is modified with a smooth transition function between low speed and high speed to make the internal state steady, then the modified LuGre model is applied for dynamic friction compensation. Then a discontinuous-projection-based desired compensation adaptive robust controller (ARC) is constructed, which makes full use of the LuGre friction model in the presence of dynamic friction effects. Comparative simulation results are conducted on a LELS simulation system. The simulation results illustrate the effectiveness of the proposed scheme.

Dynamic Systems and Control, Parts A and B, 2006

Previous research has assumed that a perfect Proton Exchange Membrane Fuel Cell (PEMFC) body temp... more Previous research has assumed that a perfect Proton Exchange Membrane Fuel Cell (PEMFC) body temperature manager is available. Maintaining this temperature at a desired value can ensure a high reaction efficiency over all operation. However, fuel cell internal body temperature control has not been specifically presented so far. This work presents such control, using a Multiple Input Single Output (MISO) fuel cell cooling system to regulate the internal body temperature of a PEMFC intended for transportation. The cooling system plant is taken from a recently developed hydrogen/air PEMFC total system model. It is linearized and used to design a series of controllers via µ-synthesis. µ-synthesis is chosen since system nonlinearities can be handled as parameter uncertainties. A controller must coordinate the desired fuel cell internal temperature and commanded mass flow rates of the coolant and cooling air. Each linear controller is created for a segment of the expected current density range. Plant parameters are expected to vary over their linearized values in each segment. Also, a common set of µ-synthesis weighting functions has been developed to ease controller design at different operating points. Thus, the nonlinear cooling subsystem can be controlled with a series of current density scheduled linear controllers. Current density step change simulations are presented to compare the controller closed loop performance and open loop response which uses cooling system flow rates taken from an optimal steady state solution of the whole fuel cell system. Furthermore, a closed loop sinusoid response is also given. These show that the closed loop driven * Address all correspondence to this author. internal fuel cell temperature will vary little during operation. However, this will only be true over the range that the cooling system is required to be active.

2007 American Control Conference, 2007

Considering rather severe parametric uncertainties and nonlinear uncertainties exist in the dynam... more Considering rather severe parametric uncertainties and nonlinear uncertainties exist in the dynamic model of pneumatic muscles driven parallel manipulator, a discontinuous projection-based adaptive robust control strategy (ARC) is adopted to effectively handle the effect of various parameter variations of the system and hard-to-model nonlinearities such as the friction forces of the pneumatic muscles and external disturbances of the entire pneumatic system to achieve remarkably precise posture trajectory control. Experimental results are obtained to illustrate the effectiveness of the proposed adaptive robust controller.

2010 IEEE International Conference on Robotics and Automation, 2010

Cable conduit actuation provides a simple yet dexterous mode of power transmission for remote act... more Cable conduit actuation provides a simple yet dexterous mode of power transmission for remote actuation. However, they are not preferred because of the nonlinearities arising from friction and cable compliance which lead to backlash type of behavior. Unlike most of the current research in backlash control which generally assumes no knowledge of one of the intermediate states, the controller design in this case can be significantly simplified if output feedback of the system is available. This paper uses a simple feedforward control law for backlash compensation. A novel smooth backlash inverse is proposed, which takes the physical limitations of the actuator in consideration, unlike other designs, and thus makes it more intuitive to use. Implementation of this inverse on physical systems can also improve the system performance over the theoretical exact inverse, as well as other existing smooth inverse designs. Improvement in the performance is shown through experiments on a robot arm of Laprotek surgical system as well as on an experimental setup using polymeric cables for actuation.

Volume 2: Systems; Micro and Nano Technologies; Sustainable Manufacturing, 2013

ABSTRACT The contour error of machining processes is defined as the difference between the desire... more ABSTRACT The contour error of machining processes is defined as the difference between the desired and actual produced shape. Two major factors contributing to contour error are axis position error and tool deflection. A large amount of research work formulates the contour error in convenient locally defined task coordinate frames that are subject to significant approximation error. The more accurate global task coordinate frame (GTCF) can be used, but transforming the control problem to the GTCF leads to a highly nonlinear control problem. An adaptive robust control (ARC) approach is designed to control machine position in the GTCF, while directly accounting for tool deflection, to minimize the contour error. The combined GTCF/ARC approach is experimentally validated by applying the control to circular contours on a three axis milling machine. The results show that the proposed approach reduces contour error in all cases tested.

a b s t r a c t Rather severe parametric uncertainties and uncertain nonlinearities exist in the ... more a b s t r a c t Rather severe parametric uncertainties and uncertain nonlinearities exist in the dynamic modeling of a parallel manipulator driven by pneumatic muscles. Those uncertainties not only come from the time- varying friction forces and the static force modeling errors of pneumatic muscles but also from the inherent complex nonlinearities and unknown disturbances of the parallel manipulator. In this paper, a discontinuous projection-based adaptive robust control strategy is adopted to compensate for both the parametric uncertainties and uncertain nonlinearities of a three-pneumatic-muscles-driven parallel manipulator to achieve precise posture trajectory tracking control. The resulting controller effectively handles the effects of various parameter variations and the hard-to-model nonlinearities such as the friction forces of the pneumatic muscles. Simulation and experimental results are obtained to illustrate the effectiveness of the proposed adaptive robust controller.

Dynamic Systems and Control, 2002

In the fall of 2001 we implemented a new controller design project in our Junior/Senior level con... more In the fall of 2001 we implemented a new controller design project in our Junior/Senior level controls class in Mechanical Engineering at Purdue University. The old project, which involved the identification and control of a “black box”, failed to challenge and motivate students. Our new project is the design of a controller for the point-to-point motion of a gantry crane system. Student teams modeled the gantry crane and developed a controller to meet several performance specifications. The designs were implemented in Simulink with MATLAB’s Real-Time Workshop. A competition served to further motivate the students. In the end we were very impressed with the great effort the students gave and the quality of their designs. Each group presented their design and most students stayed and asked questions for several hours.

2007 IEEE/ASME international conference on advanced intelligent mechatronics, 2007

This paper presents the problem of fault detection in the presence of input unmodeled dynamics. T... more This paper presents the problem of fault detection in the presence of input unmodeled dynamics. There are mainly two sources of uncertainties for a system in addition to external disturbances: parametric uncertainties and unmodeled dynamics. For nonlinear systems, the problem of fault detection and isolation has been studied under the assumption that modeling uncertainty can be bounded by an a priori known function. Many robust algorithms have been designed based on this assumption. But, the problem of fault detection in the presence of dynamic uncertainties for nonlinear systems has not been addressed by many researchers. The goal of this work is to focus on the problem of actuator fault detection in the presence of input unmodeled dynamics. We use stateestimation errors as residuals for fault detection and monitoring the system for any off-nominal behavior. A rigorous analysis is done to understand the effects of unmodeled dynamics on the process of fault detection. Based on the analysis, we derive a threshold function for the purpose of fault detection, which can decouple the effects of fault and unmodeled dynamics. Finally, simulations are performed to show the effectiveness of the proposed method.

Dynamic Systems and Control, Parts A and B, 2006

The combined use of Variable Geometry Turbine (VGT) and Exhaust Gas Recirculation (EGR) gives us ... more The combined use of Variable Geometry Turbine (VGT) and Exhaust Gas Recirculation (EGR) gives us an opportunity to reduce emissions, without compromising the need to generate more power. In the present work, a multivariable approach is used to tackle the EGR-VGT actuator control problem. A linear multivariable controller is designed using Lyapunov's Indirect Method, based on the Jacobian matrix of the system. Then, some stronger conditions are sought to be satisfied by the Jacobian matrix, which would ensure the Global Asymptotic Stability of the system. These conditions are derived using Nonlinear Contraction Analysis. Finally, simulations are performed on a simplified model with three states to evaluate the performance of the controllers.

2010 11th IEEE International Workshop on Advanced Motion Control (AMC), 2010

The ever increasingly stringent performance requirements of modern mechanical systems have forced... more The ever increasingly stringent performance requirements of modern mechanical systems have forced control engineers to look beyond traditional linear control theory for more advanced nonlinear controllers. During the past decade, a mathematically rigorous nonlinear adaptive robust control (ARC) theory has been developed and has been experimentally demonstrated achieving significant performance improvement in a number of motion control applications. This plenary paper first uses a simple motion control problem as an example to bring out the conceptual connection and nonlinear extension of the widely used PID controller structure to the developed ARC approach. Through this example, some of the key underlying working mechanisms of the ARC theory can be grasped easily. The paper then highlights how major issues in the precision motion control can be handled systematically and effectively with the ARC framework. The issues considered include (i) large variations of physical parameters of a system; (ii) unknown nonlinearities such as cogging and ripple forces of linear motors; (iii) dynamic uncertain nonlinearities with non-uniformly detectable unmeasured internal states (e.g., friction described by dynamic models in high precision motion controls); and (iv) control input saturation due to limited capacity of physical actuators. The precision motion control of a linear motor driven high-speed/high-acceleration industrial gantry is used as a case study and comparative experimental results are presented to illustrate the achievable performance and limitations of various ARC controllers in implementation.

IEEE/ASME Transactions on Mechatronics, 2000

High performance robust motion control of single-rod hydraulic actuators is considered. In contra... more High performance robust motion control of single-rod hydraulic actuators is considered. In contrast t o the double-rod hydraulic actuators studied previously, the two chambers of a single-rod hydraulic actuator have different areas. As a result, the dynamic equations describing the pressure changes in the two chambers cannot be combined into a single load pressure equation. This complicates the controller design since it not only increases the dimension of the system to be dealt with but also brings in the stability issue of the added internal dynamics. A discontinuous projection based adaptive robust controller is constructed. The controller is able to take into account not only the effect of parameter variations coming from the inertia load and various hydraulic parameters but also the effect of hardto-model nonlinearities such as uncompensated friction forces and external disturbances. Extensive experimental results are obtained for the swing motion control of a hydraulic arm. I n comparison to a state-of-the-art industrial motion controller, the proposed ARC algorithm achieves more than a magnitude reduction of tracking errors. Furthermore, during constant velocity and regulation periods, the ARC controller reduces the tracking errors almost down to the measurement resolution level.

Many robotic systems, like surgical robots, robotic hands, and exoskeleton robots, use cable pass... more Many robotic systems, like surgical robots, robotic hands, and exoskeleton robots, use cable passing through conduits to actuate remote instruments. Cable actuation simplifies the design and allows the actuator to be located at a convenient location, away from the end effector. However, nonlinear frictions between the cable and the conduit account for major losses in tension transmission across the cable, and a model is needed to characterize their effects in order to analyze and compensate for them. Although some models have been proposed in the literature, they are lumped parameter based and restricted to the very special case of a single cable with constant conduit curvature and constant pretension across the cable only. This paper proposes a mathematically rigorous distributed parameter model for cable-conduit actuation with any curvature and initial tension profile across the cable. The model, which is described by a set of partial differential equations in the continuous time-domain, is also discretized for the effective numerical simulation of the cable motion and tension transmission across the cable. Unlike the existing lumped-parameter-based models, the resultant discretized model enables one to accurately simulate the partial-moving/partial-sticking cable motion of the cable-conduit actuation with any curvature and initial tension profile. The model is further extended to cable-conduit actuation in pull-pull configuration using a pair of cables. Various simulations results are presented to reveal the unique phenomena like backlash, cable slacking, interaction between the two cables, and other nonlinear behaviors associated with the cable conduits in pullpull configuration. These results are verified by experiments using two dc motors coupled with a cable-conduit pair. The experimental setup has been prepared to emulate a typical cable-actuated robotic system. Experimental results are compared with the simulations and various implications are discussed.

2008 IEEE International Conference on Robotics and Automation, 2008

Many surgical robots use cable-conduit pairs in a pull-pull configuration to actuate the instrume... more Many surgical robots use cable-conduit pairs in a pull-pull configuration to actuate the instruments and transmit power into the patient's body. Friction between the cable and the conduit makes the system nonlinear and accounts for major losses in tension transmission across the cable. This paper proposes an analytical model for a similar cable-conduit system and formulates the load transmission characteristics. The dynamic model uses discrete elements with friction losses and cable stretch calculated for each of the segments. The simulations predict backlash, cable slacking, and other nonlinear behavior. These results are verified with an experiment using two DC motors coupled with a cable-conduit pair. The drive motor is run in position control mode, while the load motor simulates a passive environment torsional spring. Experimental results are compared with the simulation and various implications are discussed.

Adaptive motion and force control of manipulators in constrained motion in the presence of parame... more Adaptive motion and force control of manipulators in constrained motion in the presence of parametric uncertainties both in the robot and contact surfaces is solved in this paper. A new constrained dynamic model is obtained to account for the effect of contact surface friction. An adaptive law is suggested with unknown parameters updated by both motion and force tracking errors

Dynamic Systems and Control, Parts A and B, 2005

This paper presented multi-objective optimization of tip tracking control for non-collocated flex... more This paper presented multi-objective optimization of tip tracking control for non-collocated flexible beam. The desired trajectory is specified at the tip displacement of the flexible struc- ture, which undergoes translation base motion actuated by a lin- ear motor. The system model is first formulated from modal truncation approach for the flexible structure representing a sin- gle Cartesian robot manipulator. The linear system model of the flexible structure always has structural uncertainties. Robust sta- bility and robust performance on tip tracking can be expressed as H2/H∞ norm constraints, which are converted into the Linear Matrix Inequality (LMI). The multi-objective controller design is solved by the convex minimization. In order to reduce the con- servatism generated when the same Lyapunov matrix is selected, the Lyapunov matrix is scaled for different norm constraints. Simulation results have demonstrated favorable tip tracking of the proposed robust controller.

Dynamic Systems and Control, Parts A and B, 2006

2006 American Control Conference, 2006

ABSTRACT The back-stepping designs based on confine functions are suggested for the robust output... more ABSTRACT The back-stepping designs based on confine functions are suggested for the robust output-feedback global stabilization of a class of nonlinear continuous systems; the proposed stabilizer is efficient for the nonlinear continuous systems confined by a bound function, the nonlinearities of the systems may be of varied forms or uncertain; the designed stabilizer is robust means that a class of nonlinear continuous systems can be stabilized by the same output feedback stabilization schemes: numerical simulation examples are given.

2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2010

This paper proposes a sensorless force estimation method for the end effector tip of a surgical r... more This paper proposes a sensorless force estimation method for the end effector tip of a surgical robot instrument. Due to various size and safety constraints related to the surgical robot instrument, it is difficult to measure the reaction force at the instrument tip. This paper presents a method of estimating the reaction force of the surgical robot instrument without sensors and attempts to use state observer of control algorithm. Sliding mode control with sliding perturbation observer (SMCSPO) is used to drive the instrument, where the sliding perturbation observer (SPO) computes the amount of perturbation defined as the combination of the uncertainties and nonlinear terms where the major uncertainties arise from the reaction force. Based on this idea, this paper proposes a method to estimate the reaction force on the end-effector tip of the surgical robot instruments using only SPO and encoder without any additional sensors. To evaluate the validity of this paper, experiment was performed and the results showed that the estimated force computed from SPO is similar to the actual force.

2010 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, 2010

Linear electrical loading system (LELS) driven by electrical cylinder with permanent magnet synch... more Linear electrical loading system (LELS) driven by electrical cylinder with permanent magnet synchronous motor (PMSM) offers several advantages of high transmission efficiency and high precision positioning, however these advantages are obtained at the expense of larger friction in mechanism and added difficulties in controlling such a force servo system. To address the problems, the LuGre friction model is modified with a smooth transition function between low speed and high speed to make the internal state steady, then the modified LuGre model is applied for dynamic friction compensation. Then a discontinuous-projection-based desired compensation adaptive robust controller (ARC) is constructed, which makes full use of the LuGre friction model in the presence of dynamic friction effects. Comparative simulation results are conducted on a LELS simulation system. The simulation results illustrate the effectiveness of the proposed scheme.

Dynamic Systems and Control, Parts A and B, 2006

Previous research has assumed that a perfect Proton Exchange Membrane Fuel Cell (PEMFC) body temp... more Previous research has assumed that a perfect Proton Exchange Membrane Fuel Cell (PEMFC) body temperature manager is available. Maintaining this temperature at a desired value can ensure a high reaction efficiency over all operation. However, fuel cell internal body temperature control has not been specifically presented so far. This work presents such control, using a Multiple Input Single Output (MISO) fuel cell cooling system to regulate the internal body temperature of a PEMFC intended for transportation. The cooling system plant is taken from a recently developed hydrogen/air PEMFC total system model. It is linearized and used to design a series of controllers via µ-synthesis. µ-synthesis is chosen since system nonlinearities can be handled as parameter uncertainties. A controller must coordinate the desired fuel cell internal temperature and commanded mass flow rates of the coolant and cooling air. Each linear controller is created for a segment of the expected current density range. Plant parameters are expected to vary over their linearized values in each segment. Also, a common set of µ-synthesis weighting functions has been developed to ease controller design at different operating points. Thus, the nonlinear cooling subsystem can be controlled with a series of current density scheduled linear controllers. Current density step change simulations are presented to compare the controller closed loop performance and open loop response which uses cooling system flow rates taken from an optimal steady state solution of the whole fuel cell system. Furthermore, a closed loop sinusoid response is also given. These show that the closed loop driven * Address all correspondence to this author. internal fuel cell temperature will vary little during operation. However, this will only be true over the range that the cooling system is required to be active.

2007 American Control Conference, 2007

Considering rather severe parametric uncertainties and nonlinear uncertainties exist in the dynam... more Considering rather severe parametric uncertainties and nonlinear uncertainties exist in the dynamic model of pneumatic muscles driven parallel manipulator, a discontinuous projection-based adaptive robust control strategy (ARC) is adopted to effectively handle the effect of various parameter variations of the system and hard-to-model nonlinearities such as the friction forces of the pneumatic muscles and external disturbances of the entire pneumatic system to achieve remarkably precise posture trajectory control. Experimental results are obtained to illustrate the effectiveness of the proposed adaptive robust controller.

2010 IEEE International Conference on Robotics and Automation, 2010

Cable conduit actuation provides a simple yet dexterous mode of power transmission for remote act... more Cable conduit actuation provides a simple yet dexterous mode of power transmission for remote actuation. However, they are not preferred because of the nonlinearities arising from friction and cable compliance which lead to backlash type of behavior. Unlike most of the current research in backlash control which generally assumes no knowledge of one of the intermediate states, the controller design in this case can be significantly simplified if output feedback of the system is available. This paper uses a simple feedforward control law for backlash compensation. A novel smooth backlash inverse is proposed, which takes the physical limitations of the actuator in consideration, unlike other designs, and thus makes it more intuitive to use. Implementation of this inverse on physical systems can also improve the system performance over the theoretical exact inverse, as well as other existing smooth inverse designs. Improvement in the performance is shown through experiments on a robot arm of Laprotek surgical system as well as on an experimental setup using polymeric cables for actuation.

Volume 2: Systems; Micro and Nano Technologies; Sustainable Manufacturing, 2013

ABSTRACT The contour error of machining processes is defined as the difference between the desire... more ABSTRACT The contour error of machining processes is defined as the difference between the desired and actual produced shape. Two major factors contributing to contour error are axis position error and tool deflection. A large amount of research work formulates the contour error in convenient locally defined task coordinate frames that are subject to significant approximation error. The more accurate global task coordinate frame (GTCF) can be used, but transforming the control problem to the GTCF leads to a highly nonlinear control problem. An adaptive robust control (ARC) approach is designed to control machine position in the GTCF, while directly accounting for tool deflection, to minimize the contour error. The combined GTCF/ARC approach is experimentally validated by applying the control to circular contours on a three axis milling machine. The results show that the proposed approach reduces contour error in all cases tested.

a b s t r a c t Rather severe parametric uncertainties and uncertain nonlinearities exist in the ... more a b s t r a c t Rather severe parametric uncertainties and uncertain nonlinearities exist in the dynamic modeling of a parallel manipulator driven by pneumatic muscles. Those uncertainties not only come from the time- varying friction forces and the static force modeling errors of pneumatic muscles but also from the inherent complex nonlinearities and unknown disturbances of the parallel manipulator. In this paper, a discontinuous projection-based adaptive robust control strategy is adopted to compensate for both the parametric uncertainties and uncertain nonlinearities of a three-pneumatic-muscles-driven parallel manipulator to achieve precise posture trajectory tracking control. The resulting controller effectively handles the effects of various parameter variations and the hard-to-model nonlinearities such as the friction forces of the pneumatic muscles. Simulation and experimental results are obtained to illustrate the effectiveness of the proposed adaptive robust controller.