G. Mathijssen - Academia.edu (original) (raw)
Papers by G. Mathijssen
2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013
Future robots will need to perform complex and versatile tasks comparable to those of humans. Due... more Future robots will need to perform complex and versatile tasks comparable to those of humans. Due to the unavailability of suitable actuators, however, novel intelligent and agile robots are often restricted in their performances and development. The limited output torque range and low energy efficiency of current robotic actuators are the main bottlenecks. We have developed a SPEA with intermittent mechanism that addresses these problems. The SPEA is a novel compliant actuator concept that enables variable recruitment of parallel elastic elements and adaptive load cancellation. This paper describes how a SPEA lowers the motor torque and increases the energy efficiency. Experiments on the first proof of concept set-up endorse the practicability of the SPEA concept and the modeled trend of a lowered motor torque and increased energy efficiency. We expect that features of the biologically inspired SPEA with intermittent mechanism will prove exceedingly useful for robotics applications in the future.
Actuators, 2013
The majority of the commercial transtibial prostheses are purely passive devices. They store ener... more The majority of the commercial transtibial prostheses are purely passive devices. They store energy in an elastic element during the beginning of a step and release it at the end. A 75 kg human, however, produces on average 26 J of energy during one stride at the ankle joint when walking at normal cadence and stores/releases 9 J of energy, contributing to energy efficient locomotion. According to Winter, a subject produces on average of 250 W peak power at a maximum joint torque of 125 Nm. As a result, powering a prosthesis with traditional servomotors leads to excessive motors and gearboxes at the outer extremities of the legs. Therefore, research prototypes use series elastic actuation (SEA) concepts to reduce the power requirements of the motor. In the paper, it will be shown that SEAs are able to reduce the power of the electric motor, but not the torque. To further decrease the motor size, a novel human-centered actuator concept is developed, which is inspired by the variable recruitment of muscle fibers of a human muscle. We call this concept series-parallel elastic actuation (SPEA), and the actuator consists of multiple parallel springs, each connected to an intermittent mechanism with internal locking and a single motor. As a result, the motor torque requirements can be lowered and the efficiency drastically increased. In the paper, the novel actuation concept is explained, and a comparative study between a stiff motor, an SEA and an SPEA, which all aim at mimicking human ankle behavior, is performed.
5th IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics, 2014
Among the many features of muscles, their softness, (the ability to deform to accommodate uncerta... more Among the many features of muscles, their softness, (the ability to deform to accommodate uncertainty in the environment), and their ability to continue functioning despite disturbances, even partial damage, are qualities one would desire to see in robotic actuators. These properties are intimately related to the manner in which muscles work since they arise from the progressive recruitment of many motor units. This differs greatly from current robotic actuator technologies. We present an actuation platform prototype that can support experimental validation of algorithms for muscle fiber recruitment-inspired control, and where further ways to exploit discretization and redundancy in muscle-like control can be discovered. This platform, like muscles, is composed of discretely activated motor units with an integrated compliant coupling. The modular, cellular structure endows the actuator with good resilience in response to damage. It can also be repaired or modified to accommodate changing requirements in situ rather than replaced. Several performance metrics particular to muscle-like actuators are introduced and calculated for one of these units. The prototype has a blocked force of 2.51 N, a strain rate of 21.1 %, and has an input density of 5.46 ×10 3 motor units per square meter. It consumes 18 W of electrical power during a full isometric contraction. The actuator unit is 41.0 mm 3 in size. The force during isometric contractions as it varies with activation is evaluated experimentally for two configurations of modules.
IEEE/ASME Transactions on Mechatronics, 2000
The development and control of Variable Stiffness Actuators (VSAs) led to the capability of embod... more The development and control of Variable Stiffness Actuators (VSAs) led to the capability of embodying physical principles of safety and energy-efficiency compared to traditional stiff servomotors. However, the output torque range and efficiency of servomotors and VSAs are still insufficient which hinders the development of machines with performances comparable to a human. We have developed a novel compliant actuation concept, Series-Parallel Elastic Actuation (SPEA), that addresses these problems. The novelty being the variable recruitment of parallel elastic elements and adaptive load cancellation. In this paper we propose the use of multiple dephased mutilated gears with locking ring and plate, as intermittent mechanisms, linked in parallel to the motor. As a result, the motor torque requirements can be lowered, as such the motor can be downscaled and the efficiency can be drastically increased. After an abstract description of the SPEA concept and an outline of the biological basis, we present the first unidirectional SPEA Proof of Concept (PoC) set-up. Experiments on this PoC set-up endorse the feasibility of the SPEA concept. The results match the modeled trend of a lowered motor torque and increased energy efficiency.
ABSTRACT Natural organisms have a unique property not yet available in robotics, a self-healing (... more ABSTRACT Natural organisms have a unique property not yet available in robotics, a self-healing (SH) ability. This powerful biological healing function has inspired chemists to impart similar properties to synthetic materials to create “self-healing materials”. Recent development in SH-polymers made us investigate the potential of using these materials in robotics, and more specifically in compliant actuator.
2013 IEEE/RSJ International Conference on Intelligent Robots and Systems, 2013
Future robots will need to perform complex and versatile tasks comparable to those of humans. Due... more Future robots will need to perform complex and versatile tasks comparable to those of humans. Due to the unavailability of suitable actuators, however, novel intelligent and agile robots are often restricted in their performances and development. The limited output torque range and low energy efficiency of current robotic actuators are the main bottlenecks. We have developed a SPEA with intermittent mechanism that addresses these problems. The SPEA is a novel compliant actuator concept that enables variable recruitment of parallel elastic elements and adaptive load cancellation. This paper describes how a SPEA lowers the motor torque and increases the energy efficiency. Experiments on the first proof of concept set-up endorse the practicability of the SPEA concept and the modeled trend of a lowered motor torque and increased energy efficiency. We expect that features of the biologically inspired SPEA with intermittent mechanism will prove exceedingly useful for robotics applications in the future.
Actuators, 2013
The majority of the commercial transtibial prostheses are purely passive devices. They store ener... more The majority of the commercial transtibial prostheses are purely passive devices. They store energy in an elastic element during the beginning of a step and release it at the end. A 75 kg human, however, produces on average 26 J of energy during one stride at the ankle joint when walking at normal cadence and stores/releases 9 J of energy, contributing to energy efficient locomotion. According to Winter, a subject produces on average of 250 W peak power at a maximum joint torque of 125 Nm. As a result, powering a prosthesis with traditional servomotors leads to excessive motors and gearboxes at the outer extremities of the legs. Therefore, research prototypes use series elastic actuation (SEA) concepts to reduce the power requirements of the motor. In the paper, it will be shown that SEAs are able to reduce the power of the electric motor, but not the torque. To further decrease the motor size, a novel human-centered actuator concept is developed, which is inspired by the variable recruitment of muscle fibers of a human muscle. We call this concept series-parallel elastic actuation (SPEA), and the actuator consists of multiple parallel springs, each connected to an intermittent mechanism with internal locking and a single motor. As a result, the motor torque requirements can be lowered and the efficiency drastically increased. In the paper, the novel actuation concept is explained, and a comparative study between a stiff motor, an SEA and an SPEA, which all aim at mimicking human ankle behavior, is performed.
5th IEEE RAS/EMBS International Conference on Biomedical Robotics and Biomechatronics, 2014
Among the many features of muscles, their softness, (the ability to deform to accommodate uncerta... more Among the many features of muscles, their softness, (the ability to deform to accommodate uncertainty in the environment), and their ability to continue functioning despite disturbances, even partial damage, are qualities one would desire to see in robotic actuators. These properties are intimately related to the manner in which muscles work since they arise from the progressive recruitment of many motor units. This differs greatly from current robotic actuator technologies. We present an actuation platform prototype that can support experimental validation of algorithms for muscle fiber recruitment-inspired control, and where further ways to exploit discretization and redundancy in muscle-like control can be discovered. This platform, like muscles, is composed of discretely activated motor units with an integrated compliant coupling. The modular, cellular structure endows the actuator with good resilience in response to damage. It can also be repaired or modified to accommodate changing requirements in situ rather than replaced. Several performance metrics particular to muscle-like actuators are introduced and calculated for one of these units. The prototype has a blocked force of 2.51 N, a strain rate of 21.1 %, and has an input density of 5.46 ×10 3 motor units per square meter. It consumes 18 W of electrical power during a full isometric contraction. The actuator unit is 41.0 mm 3 in size. The force during isometric contractions as it varies with activation is evaluated experimentally for two configurations of modules.
IEEE/ASME Transactions on Mechatronics, 2000
The development and control of Variable Stiffness Actuators (VSAs) led to the capability of embod... more The development and control of Variable Stiffness Actuators (VSAs) led to the capability of embodying physical principles of safety and energy-efficiency compared to traditional stiff servomotors. However, the output torque range and efficiency of servomotors and VSAs are still insufficient which hinders the development of machines with performances comparable to a human. We have developed a novel compliant actuation concept, Series-Parallel Elastic Actuation (SPEA), that addresses these problems. The novelty being the variable recruitment of parallel elastic elements and adaptive load cancellation. In this paper we propose the use of multiple dephased mutilated gears with locking ring and plate, as intermittent mechanisms, linked in parallel to the motor. As a result, the motor torque requirements can be lowered, as such the motor can be downscaled and the efficiency can be drastically increased. After an abstract description of the SPEA concept and an outline of the biological basis, we present the first unidirectional SPEA Proof of Concept (PoC) set-up. Experiments on this PoC set-up endorse the feasibility of the SPEA concept. The results match the modeled trend of a lowered motor torque and increased energy efficiency.
ABSTRACT Natural organisms have a unique property not yet available in robotics, a self-healing (... more ABSTRACT Natural organisms have a unique property not yet available in robotics, a self-healing (SH) ability. This powerful biological healing function has inspired chemists to impart similar properties to synthetic materials to create “self-healing materials”. Recent development in SH-polymers made us investigate the potential of using these materials in robotics, and more specifically in compliant actuator.