Designing an optimal control strategy for a mobile manipulator and its application by considering the effect of uncertainties and wheel slipping

Abstract

This article seeks to develop the dynamic model of a mobile robot for controlling purposes while the effects of uncertainties and longitudinal and lateral slip are assumed. The rise in the number of state variables and considering the effects of nonlinear parameters due to slip modeling can complicate the control procedure of wheeled mobile manipulators. In addition, the existence of uncertainties as well as holonomic and nonholonomic constraints would increase this complexity even more. On the one side, as wheels are considered to slip, unwanted movements due to slippage affect the movement of the manipulator and the manipulator may not be able to track the desired path. On the other side, the movement of weighted links of the manipulator constantly changes the normal forces of the wheels. As traction forces are dependent on these normal forces, the path tracked by the platform would be affected. Given these conditions, employing a robust control methodology and developing an optimal algorithm to reduce the effects of uncertainties and wheels slip seems mandatory. To this aim, a sliding mode control (SMC) strategy is formulated in this study. Furthermore, the suggested algorithm is optimized using a state-dependent Riccati equation to reduce the consumed torque and increase the accuracy of the system. Simulations are conducted, and the presented algorithm is also checked with the experimental setup of a Scout robot. Simulation results show that the optimal sliding mode control (OSMC) successfully decreases sudden jumps due to slippage in the system. In addition, the consumed power of wheels and arm for SMC decreases from 9.15 and 1.02 N⋅m to, respectively, 1.46 and 0.54 N⋅m for OSMC.

A general update rule for Lyapunov‐based adaptive control of mobile robots with wheel slip

“…When longitudinal slip is present, the robot velocity vector 𝜂(t) is given by (6). Substituting ( 6) into (11), one obtains…”

“…Controller design methods for differential-drive mobile robots are typically based on either kinetic or kinematic models. 10,11 In each of these modeling paradigms, wheel slip is treated differently. In kinetic models, which relate robot accelerations to wheel torques, modeling the slip phenomenon is generally complex, accounting for factors such as wheel temperature, thread pattern, and camber angle.…”

“…One viable solution to this issue is to explicitly incorporate the slip effects into the controller design. Controller design methods for differential‐drive mobile robots are typically based on either kinetic or kinematic models 10,11 . In each of these modeling paradigms, wheel slip is treated differently.…”

Robust decomposed system control for an electro‐mechanical linear actuator mechanism under input constraints

“…where the resistance of the stator winding is denoted as R s . To eliminate the dependence of the PMSM's three-phase voltage on the rotor angle, the Park transformation can be utilized, as it converts the voltage from the ABC frame to the dq0 frame, as illustrated in (4).…”

“…[1][2][3] Mobile manipulators, which are robotic arms mounted on wheeled platforms for industrial use, can benefit from the development of BEVs, as they are capable of performing a wide range of tasks in various environments, from manufacturing and logistics to search and rescue operations and beyond. 4 The on-board robotic arms of mobile manipulators can be equipped with hydraulic actuators, to enable their movement and manipulation capabilities, as they are commonly used in such scenarios due to their high power-to-weight ratio. Despite representing a mainstay in numerous industries for decades, the use of hydraulic actuators in mobile manipulators presents several challenges and limitations, the primary of which is that they are energy-inefficient.…”