Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Safe Force/Position Tracking Control via Control Barrier Functions for Floating Base Mobile Manipulator Systems

Maryam Sharifi, Shahab Heshmati-Alamdari

TL;DR

This work tackles safe force/position tracking for floating-base mobile manipulators during compliant planar contact. It advances a control framework that integrates zeroing control barrier functions with a robust quadratic-programming-based controller to enforce safety at both kinematic and dynamic levels, accommodating model uncertainties and variable contact stiffness. The method ensures forward invariance of safety sets and provides real-time feasibility through QP-based solutions, even under disturbances. Simulations on a UVMS demonstrate maintained contact, bounded interaction forces, and adherence to safety constraints, highlighting practical applicability to tasks like welding that demand precise and safe environmental interaction.

Abstract

This paper introduces a safe force/position tracking control strategy designed for Free-Floating Mobile Manipulator Systems (MMSs) engaging in compliant contact with planar surfaces. The strategy uniquely integrates the Control Barrier Function (CBF) to manage operational limitations and safety concerns. It effectively addresses safety-critical aspects in the kinematic as well as dynamic level, such as manipulator joint limits, system velocity constraints, and inherent system dynamic uncertainties. The proposed strategy remains robust to the uncertainties of the MMS dynamic model, external disturbances, or variations in the contact stiffness model. The proposed control method has low computational demand ensures easy implementation on onboard computing systems, endorsing real-time operations. Simulation results verify the strategy's efficacy, reflecting enhanced system performance and safety.

Safe Force/Position Tracking Control via Control Barrier Functions for Floating Base Mobile Manipulator Systems

TL;DR

This work tackles safe force/position tracking for floating-base mobile manipulators during compliant planar contact. It advances a control framework that integrates zeroing control barrier functions with a robust quadratic-programming-based controller to enforce safety at both kinematic and dynamic levels, accommodating model uncertainties and variable contact stiffness. The method ensures forward invariance of safety sets and provides real-time feasibility through QP-based solutions, even under disturbances. Simulations on a UVMS demonstrate maintained contact, bounded interaction forces, and adherence to safety constraints, highlighting practical applicability to tasks like welding that demand precise and safe environmental interaction.

Abstract

This paper introduces a safe force/position tracking control strategy designed for Free-Floating Mobile Manipulator Systems (MMSs) engaging in compliant contact with planar surfaces. The strategy uniquely integrates the Control Barrier Function (CBF) to manage operational limitations and safety concerns. It effectively addresses safety-critical aspects in the kinematic as well as dynamic level, such as manipulator joint limits, system velocity constraints, and inherent system dynamic uncertainties. The proposed strategy remains robust to the uncertainties of the MMS dynamic model, external disturbances, or variations in the contact stiffness model. The proposed control method has low computational demand ensures easy implementation on onboard computing systems, endorsing real-time operations. Simulation results verify the strategy's efficacy, reflecting enhanced system performance and safety.
Paper Structure (9 sections, 2 theorems, 36 equations, 4 figures)

This paper contains 9 sections, 2 theorems, 36 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Problem Formulation
  3. Control Methodology
  4. Control Design
  5. Kinematic Safety-Critical Control
  6. Control Barrier Function Based Velocity Control
  7. Kinematic-Consistent Dynamic Safety-Critical Control
  8. Simulation results
  9. Conclusions

Key Result

Lemma 1

Let the sets $\mathcal{S}_i$, $i\in\{f,y,z,o_1,o_2,o_3\}$ as the superlevel set of continuously differentiable functions $b_i:\mathbb{R}\to\mathbb{R}$ defined in barrier1. Then, the safety-critical velocity based controller from the quadratic problem s.t. in which $\mkern 1.0mu\overline{\mkern-1.0mu\boldsymbol{M}\mkern-1.0mu}\mkern 1.0mu:=[\mkern 1.0mu\overline{\mkern-1.0muM\mkern-1.0mu}\mkern

Figures (4)

  • Figure 1: A graphical illustration of the MMS end-effector in compliant contact with a planar surface.
  • Figure 2: The evolution of the force trajectory. The desired constant force and the actual force exerted by the UVMS are indicated by green and red color respectively.
  • Figure 3: The evolution of the errors at the first level of the proposed control scheme. The errors and performance bounds are indicated by blue and red color respectively.
  • Figure 4: The evolution of the errors at the second level of the proposed control scheme. The errors and safety bounds are indicated by blue and red color respectively.

Theorems & Definitions (6)

  • Definition 1
  • Lemma 1
  • proof
  • Definition 2
  • Theorem 1
  • proof