Abstract
These days, biomimetic and compliant actuators have been made available to the main applications of rehabilitation and assistive robotics. In this context, the interaction control of soft robots, mechatronic surgical instruments and robotic prostheses can be improved through the adoption of pneumatic artificial muscles (PAMs), a class of compliant actuators that exhibit some similarities with the structure and function of biological muscles. Together with the advantage of implementing adaptive compliance control laws, the nonlinear and hysteretic force/length characteristics of PAMs pose some challenges in the design and implementation of tracking control strategies. This paper presents a parsimonious and accurate model of the asymmetric hysteresis observed in the force response of PAMs. The model has been validated through the experimental identification of the mechanical response of a small-sized PAM where the asymmetric effects of hysteresis are more evident. Both the experimental results and a comparison with other dynamic friction models show that the proposed model could be useful to implement efficient compensation strategies for the tracking control of soft robots.
Highlights
In the field of Soft Robotics, the safety constraints involved in human–robot interaction (HRI) can be fulfilled through adjustable stiffness mechanisms actuated by compliant actuators [1]; the control of the adaptable compliance can be achieved through some control methodologies inspired by the human musculoskeletal system
A total of six parameters can be associated with the first block; this number is reduced to five by adding the constraint k1,r = k1,d = k1. Another two blocks are assigned to the descending phase and, they contribute to the pneumatic artificial muscles (PAMs) dynamics through two additional state variables and six parameters activated under the condition v < 0
The identification of the asymmetric hysteresis in PAMs is most useful to trajectory tracking and impedance control of precision servomechanisms in rehabilitation and assistive robotics applications
Summary
Soft Robotics is an emerging branch of bio-inspired robotics fostering the development of biomedical and assistive technologies as well as the design of control methodologies for the optimization of human–robot interaction (HRI) in prosthetics, rehabilitation and surgical robotics.In the field of Soft Robotics, the safety constraints involved in HRI can be fulfilled through adjustable stiffness mechanisms actuated by compliant actuators [1]; the control of the adaptable compliance can be achieved through some control methodologies inspired by the human musculoskeletal system.Among the actuation technologies implemented in the control systems of soft robots, PneumaticArtificial Muscles (PAMs) [2] are good candidates as biomimetic, light, safe and efficient actuators for rehabilitation robots, wearable exoskeleton robots and energy-efficient walking humanoids (see [3,4,5,6]).Analogously with the biological muscle, a PAM only works in the contraction direction; the “muscular activation” generating the contraction force is obtained by inflating the air chamber of the PAM. Soft Robotics is an emerging branch of bio-inspired robotics fostering the development of biomedical and assistive technologies as well as the design of control methodologies for the optimization of human–robot interaction (HRI) in prosthetics, rehabilitation and surgical robotics. In the field of Soft Robotics, the safety constraints involved in HRI can be fulfilled through adjustable stiffness mechanisms actuated by compliant actuators [1]; the control of the adaptable compliance can be achieved through some control methodologies inspired by the human musculoskeletal system. Among the actuation technologies implemented in the control systems of soft robots, Pneumatic. Artificial Muscles (PAMs) [2] are good candidates as biomimetic, light, safe and efficient actuators for rehabilitation robots, wearable exoskeleton robots and energy-efficient walking humanoids (see [3,4,5,6]). The mechanical response of the actuator exhibits an hysteretic behaviour, since the force vs
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