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Effort Sensors
Published in Clarence W. de Silva, Sensor Systems, 2016
Dynamic stiffness is defined as the ratio: (Output force)/(Input displacement), expressed in the frequency domain. Dynamic flexibility or compliance or receptance is the inverse of dynamic stiffness. Mechanical impedance is defined as the ratio: (Output force)/(Input velocity), in the frequency domain. Mobility is the inverse of mechanical impedance. Note that stiffness and impedance both relate force and motion variables in a mechanical system. The objective of impedance control is to make the impedance function equal to some specified function (without separately controlling or independently constraining the associated force and velocity variables).
Control of Robotic Systems in Contact Tasks
Published in Osita D. I. Nwokah, Yildirim Hurmuzlu, The Mechanical Systems Design Handbook, 2017
Dragoljub Šurdilović, Miomir Vukobratović
The main advantage of impedance control over force control is easier task specification and programming. A contact task is specified in terms of motion sequences, so the impedance control does not require modifications of conventional free space planning control concepts and algorithms (the programmer can take advantage of existing off-line programming). Moreover, impedance control can be activated in free space during approach motion. Thus, it can be applied for the transition to and from the constraint motion, without specific control-switching algorithms.
The realization of robotic neurorehabilitation in clinical: use of computational intelligence and future prospects analysis
Published in Expert Review of Medical Devices, 2020
Jiali Yang, Zhiqi Zhao, Chenzhen Du, Wei Wang, Qin Peng, Juhui Qiu, Guixue Wang
In addition, Azar et al. reviewed the impedance control method with regard to minimal error and good stability, where GA was adopted to enhance the safety of patients. Impedance control is an intelligent method which always guides the position and force by adjusting the mechanical impedance to the external forces generated by environmental disturbance. Its application greatly impacts the security of the trajectory [78]. Based on the previous work by FOPID controller, Ayas et al. developed and incorporated a fuzzy logic controller (FLC) with a cuckoo search algorithm (CSA). Compared with traditional PID controllers, this hybrid model reduced steady-state tracking errors by 50% [79]. Meanwhile, Silawatchananai et al. used PSO-based fixed structure H∞ control which produced better tracking performance than the conventional PID controller [80]. Compared with traditional robot controllers, these advanced controllers display better robustness and stability in the recovery of crucial factors, development of rehabilitation controls, and trajectory tracking.
Robust impedance control of robot manipulators using differential equations as universal approximator
Published in International Journal of Control, 2018
Alireza Izadbakhsh, Saeed Khorashadizadeh
Basically, two broad control approaches can be distinguished in contact problems (Almeida, Lopes, & Abreu, 1999; Kazerooni, Houpt, & Sheridan, 1986; Seraji & Colbaugh, 1997): hybrid force/position control (Khatib, 1987; Raibert & Craig, 1981) and impedance control (Hogan, 1985; Kazerooni, 1989). Hybrid force/position control is based on dividing the task-space into two separate subspaces. A control law is responsible for position control in the free space (position-controlled subspace) and another control law is designed for force control along the directions in which position is constrained (force-controlled subspace) (Filaretov & Zuev, 2008). Also, a selective matrix is used to determine the desired controller for each subspace. Widespread researches have been executed in this field (Craig & Raibert, 1979; Fanaei & Farrokhi, 2006). The second strategy is impedance control which was first introduced by Hogan. Impedance is a mechanical concept which describes the relation between force and position. It should be noted that impedance control is neither force control nor position control. In fact, impedance control objective is regulating the dynamic performance of the system and this goal is fulfilled by careful selection of impedance parameters.
Towards physical interaction-based sequential mobility assistance using latent generative model of movement state
Published in Advanced Robotics, 2021
Shunki Itadera, Taisuke Kobayashi, Jun Nakanishi, Tadayoshi Aoyama, Yasuhisa Hasegawa
In order to provide desirable physical interaction between the robot and the user, we employ an impedance-based control strategy. Impedance control approach has been widely used in robotic applications requiring safe physical interaction. One of the primary benefits of impedance control is to be able to specify the desired virtual dynamics presented to the user in human–robot interaction in a straightforward manner. In our previous work, we have employed an impedance control-based gait training strategy to provide a suitable walking load during training [24]. In [24], we have investigated the relationship between the set of (constant) impedance parameters and the physiological cost during walk.