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Motion Planning and Control of an Overactuated 4-Wheel Drive with Constrained Independent Steering

Shiyu Liu, Ilija Hadzic, Akshay Gupta, Aliasghar Arab

TL;DR

This work tackles motion planning for a four-wheel independent-steering vehicle with constrained steering, introducing discontinuity planes in velocity space to encode steering limits. A cascaded controller integrated with ROS Navigation combines a DWA-based planner with two new critics (swerve-constraint and smoothness) to favor smooth trajectories that respect steering constraints and minimize wheel flips. The approach is validated in both simulation and real hardware, showing reduced discontinuities and competitive travel times across diverse paths, with distance-based scoring typically outperforming simple scoring. The method provides a practical, implementable pathway for constrained-steering platforms and establishes a foundation for future fully dynamic, coupled-wheel control.

Abstract

This paper addresses motion planning and con- trol of an overactuated 4-wheel drive train with independent steering (4WIS) where mechanical constraints prevent the wheels from executing full 360-degree rotations (swerve). The configuration space of such a robot is constrained and contains discontinuities that affect the smoothness of the robot motion. We introduce a mathematical formulation of the steering constraints and derive discontinuity planes that partition the velocity space into regions of smooth and efficient motion. We further design the motion planner for path tracking and ob- stacle avoidance that explicitly accounts for swerve constraints and the velocity transition smoothness. The motion controller uses local feedback to generate actuation from the desired velocity, while properly handling the discontinuity crossing by temporarily stopping the motion and repositioning the wheels. We implement the proposed motion planner as an extension to ROS Navigation package and evaluate the system in simulation and on a physical robot.

Motion Planning and Control of an Overactuated 4-Wheel Drive with Constrained Independent Steering

TL;DR

This work tackles motion planning for a four-wheel independent-steering vehicle with constrained steering, introducing discontinuity planes in velocity space to encode steering limits. A cascaded controller integrated with ROS Navigation combines a DWA-based planner with two new critics (swerve-constraint and smoothness) to favor smooth trajectories that respect steering constraints and minimize wheel flips. The approach is validated in both simulation and real hardware, showing reduced discontinuities and competitive travel times across diverse paths, with distance-based scoring typically outperforming simple scoring. The method provides a practical, implementable pathway for constrained-steering platforms and establishes a foundation for future fully dynamic, coupled-wheel control.

Abstract

This paper addresses motion planning and con- trol of an overactuated 4-wheel drive train with independent steering (4WIS) where mechanical constraints prevent the wheels from executing full 360-degree rotations (swerve). The configuration space of such a robot is constrained and contains discontinuities that affect the smoothness of the robot motion. We introduce a mathematical formulation of the steering constraints and derive discontinuity planes that partition the velocity space into regions of smooth and efficient motion. We further design the motion planner for path tracking and ob- stacle avoidance that explicitly accounts for swerve constraints and the velocity transition smoothness. The motion controller uses local feedback to generate actuation from the desired velocity, while properly handling the discontinuity crossing by temporarily stopping the motion and repositioning the wheels. We implement the proposed motion planner as an extension to ROS Navigation package and evaluate the system in simulation and on a physical robot.
Paper Structure (15 sections, 15 equations, 5 figures, 3 tables)

This paper contains 15 sections, 15 equations, 5 figures, 3 tables.

Table of Contents

  1. Introduction
  2. System Architecture
  3. Steering Wheel Constraints
  4. Discontinuity Planes
  5. $\delta_{\mathrm{max}}=-\delta_{\mathrm{min}}=\frac{\pi}{2}$
  6. $\delta_{\mathrm{max}}=-\delta_{\mathrm{min}} \in (\frac{\pi}{2},\pi)$
  7. Region Signature
  8. Planner Implementation
  9. DWA Planner
  10. Swerve-Constraint Critic
  11. Smoothness Critic
  12. Experimental Results
  13. Experiments
  14. Results
  15. Conclusions

Figures (5)

  • Figure 1: A 4-wheel drive with independent steering (4WIS) robot: (a) front view of the experimental model and (b) top view diagram of the drivetrain.
  • Figure 2: Discontinuity planes in the $3D$ velocity configuration space. (a) $\Omega_{\delta}=[-\frac{\pi}{2}, \frac{\pi}{2}]$; (b) $\Omega_{\delta}=[-\frac{2\pi}{3}, \frac{2\pi}{3}]$; (c) $\Omega_{\delta}=[-\frac{3\pi}{4}, \frac{3\pi}{4}]$.
  • Figure 3: Definition of 12 continuous regions in the velocity configuration space. Note that regions with ID 8 and 10 are hidden at the bottom of the left halves of the planes. Regions with IDs 0 and 1 (red) are preferred.
  • Figure 4: Distance to the nearest discontinuity plane for a velocity vector located in region 0 and ahead of two auxiliary planes. (a) side view and (b) top view. Red markers show the original velocity vector, its projection onto the nearest auxiliary plane, followed by the projection onto the nearest discontinuity plane. The blue lines represent the resulting distance metric.
  • Figure 5: Actual robot trajectories with two baseline cases and two instances of the augmented DWA planner proposed in this paper. Discontinuity counts: baseline-1: 39 (aborted), baseline-2: 5, aug-DWA-1: 3, aug-DWA-2: 4.