Position-Based Fractional-Order Impedance Control of a 2 DOF Serial Manipulator

Abstract

SUMMARY Impedance control is one of the interaction and force control methods that has been widely applied in the research of robotics. In this paper, a new position-based fractional-order impedance control scheme is proposed and applied to a 2 DOF serial manipulator. An RR robot manipulator with full arm dynamics and its environment were designed using Matlab/Simulink. The position control of the manipulator was utilized based on computed torque control to cancel out the nonlinearities existing on the dynamic model of the robot. Parameters of classical impedance controller (CIC) and proposed fractional-order impedance controller (FOIC) were optimized in order to minimize impact forces for comparison of the results in three conditions. In CIC condition: three constant parameters of the impedance controller were optimized: in Frac_λμ condition: Only non-integer parameters of the FOIC were re-optimized after the parameters in CIC had been accepted, and in Frac_all condition: all parameters of the FOIC were re-optimized. In order to show the effectiveness of the proposed method, simulations were conducted for all cases and performance indices were computed for the interaction forces. Results showed that impacts were reduced with an improvement of 26.12% from CIC to Frac_ λμ and an improvement of 47.21% from CIC to Frac_all. The proposed scheme improves the impedance behavior and robustness showing better impact absorption performance, which is needed in many challenging robotic tasks and intelligent mechatronic devices.

Fractional order inspired iterative adaptive control

“…: refs. [16][17][18]). Besides excellent startup response of fractional order controllers (FOCs), some studies also showed that they can work more energy efficiently [19], which makes this control approach more suitable for "off grid" applications (i.e., mobile robots, drones, etc.…”

A Novel Trajectory Tracking Control with Modified Supertwisting Sliding Mode for Human-Robot Cooperation Manipulator in Assembly Line

“…Human-robot cooperative system is a nonlinear time-varying dynamic system with uncertain interference, in which the uncertainty and external interference greatly improve the complexity of the system. Many researchers have designed corresponding controllers for this technical problem, such as variable impedance control method [3], adaptive admittance controller [4], underactuated redundant low impedance method [5], and efficiency weighting strategy [6]. However, the existing methods lack ideal solutions to three main challenges: (1) the control system cannot guarantee the convergence of stable equilibrium.…”

“…(2) The robustness of human-robot cooperative system is endangered by uncertainty and external interference. (3) The nature and characteristics of external interference are difficult to identify and compensate.…”

Application of the Half-Order Derivative to Impedance Control of the 3-PUU Parallel Robot

“…Accordingly, the damping term can be defined proportional not to the first-order derivative of the endeffector error, but to a derivative with generic non-integer order µ. In the scientific literature, there are some examples of fractional-order impedance controls of robots [26,27]. This kind of impedance control generalizes to a three-dimensional system the fractional-order PD µ control scheme for SISO systems [28].…”