Joint-Space Impedance Control Using Intrinsic Parameters of Compliant Actuators and Inner Sliding Mode Torque Loop

Abstract

A new control law for joint-space impedance in robots with variable impedance actuators is presented. The objective is achieved using reduced information on high order derivatives compared to standard approaches, therefore leading to more reliable interactions with unknown environments. Most importantly, the impedance characteristic is given by the real stiffness and damping coefficients of each actuator, therefore updating strategies of the latter directly modify the system response obtained on the link side. The method is evaluated both in simulations and experiments. Additionally, the control law is also adapted for systems with series elastic actuators.

Fuzzy impedance-based control with fast terminal sliding mode force control loop for a series elastic actuator system

“…The performance of the proposed FTSMC is compared with the second-order sliding mode control (SOSMC) method in Garofalo et al (2019), while the impedance control loop is similar for both tests. The FTSMC coefficients are set as: ε 1 = 1 , ε 2 = 0 . 08 , λ = 10 , μ = 5 . 5 , ψ = 1 . 5 , ζ = 4 . 5 , and β = 2 for this experiment.…”

“…Pneumatic cylinder velocity signals of the time-varying reference trajectory test using the proposed FTSMC and the SOSMC in Garofalo et al (2019) labeled as 1 and 2.…”

“…The sensitivity of the controller is tested by applying sudden changes in the pneumatic cylinder load during run time. The air pressure of the pneumatic cylinder is changed from 0.2 MPa to 0.5 MPa after 10 seconds and back to 0.2 MPa again in t = 20 s. Here again, the performance of the proposed FTSMC is compared with the SOSMC method in Garofalo et al (2019) with the same fuzzy impedance control loop. The FTSMC and SOSMC constants are theoretically set as the same as section 4.B.…”

“…Therefore, the sliding mode control (SMC) has been studied in many practical systems as well as SEAs (Bae et al, 2010; Yin et al, 2019). Garofalo et al (2019) proposed a cascaded impedance controller with an inner sliding mode torque loop. It is the most closely related to the approach proposed in this work.…”

A Robust and Adaptive Control Method for Flexible-Joint Manipulator Capturing a Tumbling Satellite

“…In the capturing phase, the position-based impedance controller actively absorbs the impact energy. Different from 1D or 2D case in joint space [25], [26], both 3-dof translational and 3-dof rotational impedance in Cartesian space are achieved. The space manipulator is mounted on a controlled chaser, forming a free-flying space robot.…”