Human-adaptive control of series elastic actuators

Calanca, Andrea; Fiorini, Paolo

doi:10.1017/s0263574714001519

Cited by 63 publications

(31 citation statements)

References 22 publications

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“…Control design results are highly simplified, but it is not possible to guarantee any control performance. Finally, in the adaptive approach proposed in [18], the human is regarded as a second order system, whose parameters are on-line estimated, providing well-defined performance, but only when the system is coupled to a second order environment.…”

Section: Robot Measuresmentioning

confidence: 99%

Robust Force Control of Series Elastic Actuators

2014

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Force-controlled series elastic actuators (SEA) are widely used in novel human-robot interaction (HRI) applications, such as assistive and rehabilitation robotics. These systems are characterized by the presence of the "human in the loop", so that control response and stability depend on uncertain human dynamics, including reflexes and voluntary forces. This paper proposes a force control approach that guarantees the stability and robustness of the coupled human-robot system, based on sliding-mode control (SMC), considering the human dynamics as a disturbance to reject. We propose a chattering free solution that employs simple task models to obtain high performance, comparable with second order solutions. Theoretical stability is proven within the sliding mode framework, and predictability is reached by avoiding the reaching phase by design. Furthermore, safety is introduced by a proper design of the sliding surface. The practical feasibility of the approach is shown using an SEA prototype coupled with a human impedance in severe stress tests. To show the quality of the approach, we report a comparison with state-of-the-art second order SMC, passivity-based control and adaptive control solutions.

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Section: Robot Measuresmentioning

confidence: 99%

Robust Force Control of Series Elastic Actuators

2014

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“…Disturbance observer (DOB) based torque or impedance control strategies have also been proposed to improve SEA control accuracy and robustness [22]- [26]. Recently, adaptive torque or impedance controllers have been developed to guarantee predictable performance despite uncertainties or disturbance in the SEA or human side [27]- [32].…”

Section: Introductionmentioning

confidence: 99%

Passivity guaranteed stiffness control with multiple frequency band specifications for a cable-driven series elastic actuator

Zou

Sun

2019

Mechanical Systems and Signal Processing

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Impedance control and specifically stiffness control are widely applied for physical human-robot interaction. The series elastic actuator (SEA) provides inherent compliance, safety and further benefits. This paper aims to improve the stiffness control performance of a cable-driven SEA. Existing impedance controllers were designed within the full frequency domain, though human-robot interaction commonly falls in the low frequency range. We enhance the stiffness rendering performance under formulated constraints of passivity, actuator limitation, disturbance attenuation, noise rejection at their specific frequency ranges. Firstly, we reformulate this multiple frequencyband optimization problem into the H∞ synthesis framework. Then, the performance goals are quantitatively characterized by respective restricted frequency-domain specifications as norm bounds. Further, a structured controller is directly synthesized to satisfy all the competing performance requirements. Both simulation and experimental results showed that the produced controller enabled good interaction performance for each desired stiffness varying from 0 to 1 times of the physical spring constant. Compared with the passivity-based PID method, the proposed H∞ synthesis method achieved more accurate and robust stiffness control performance with guaranteed passivity.

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“…Sliding mode controllers has been used to generate the desired torque in [11] and [12]. In order to online adapt to condition changes, a model reference adaptive control(MRAC) has been presented in [13]. Futhermore, a H 2 -optimal controller *This work is supported by National High-tech R&D Program of China (863 Program) under Grant 2012AA041403, National Natural Science Foundation of China (Grant No.…”

Section: Introductionmentioning

confidence: 99%

A novel sliding mode control for series elastic actuator torque tracking with an extended disturbance observer

Wang

Sun

Yin

et al. 2015

2015 IEEE International Conference on Robotics and Biomimetics (ROBIO)

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To realize ideal force/torque source in applications such as monopod hopping robots and assistive robots, force/torque controlled series elastic actuators(SEA) are widely used components. Most of existing SEA force/torque control approaches are based on the simple SEA whose force/torque output is proportional to the position of the motor with respect to the payload, however the structure of SEAs is becoming more and more complex, which leads to a nonlinear trend in SEA models. To overcome the problem, we propose a general control method, which is not restricted by the SEA mechanical structure, to control SEA output torque based on nonlinear disturbance observer(NDOB). Specifically, the presented strategy yields the first control solution, with guaranteed theoretical analysis, to successfully address the nonlinear SEA torque control problem, with simultaneous payload angular velocity identification as an additional benefit. The tracking performance of the designed control system is theoretically ensured by Lyapunov analysis. Furthermore, taking a nonlinear SEA for instance, simulation and experimental results suggest the effectiveness and superior performance of the proposed method by comparing it with existing method.

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Human-adaptive control of series elastic actuators

Cited by 63 publications

References 22 publications

Robust Force Control of Series Elastic Actuators

Robust Force Control of Series Elastic Actuators

Passivity guaranteed stiffness control with multiple frequency band specifications for a cable-driven series elastic actuator

A novel sliding mode control for series elastic actuator torque tracking with an extended disturbance observer

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