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Single-Rod Brachiation Robot: Mechatronic Control Design and Validation of Prejump Phases

Juraj Lieskovský, Hijiri Akahane, Aoto Osawa, Jaroslav Bušek, Ikuo Mizuuchi, Tomáš Vyhlídal

TL;DR

This paper addresses energy-efficient brachiation between bars using a minimal single-rod robot equipped with a crank-slide center-of-mass actuator. It develops two complementary control strategies: a bang-bang limit-case policy for rapid energy pumping and a practical continuous policy based on input-output linearization that respects actuator torque limits. A precise nonlinear two-degree-of-freedom model is derived from Lagrangian dynamics and used to analyze potential and Coriolis energy exchanges during swing and rotation, with a state-space form for simulation. The authors validate the methods in simulation with parameter identification and demonstrate experimental verification of the continuous policy on a hardware prototype featuring a STM32 controller, an IMU, and an encoder, achieving pre-jump brachiation between bars. The work lays groundwork for jump trajectory planning and hardware improvements aimed at higher efficiency and robust operation in inspection and maintenance tasks.

Abstract

A complete mechatronic design of a minimal configuration brachiation robot is presented. The robot consists of a single rigid rod with gripper mechanisms attached to both ends. The grippers are used to hang the robot on a horizontal bar on which it swings or rotates. The motion is imposed by repositioning the robot's center of mass, which is performed using a crank-slide mechanism. Based on a non-linear model, an optimal control strategy is proposed, for repositioning the center of mass in a bang-bang manner. Consequently, utilizing the concept of input-output linearization, a continuous control strategy is proposed that takes into account the limited torque of the crank-slide mechanism and its geometry. An increased attention is paid to energy accumulation towards the subsequent jump stage of the brachiation. These two strategies are validated and compared in simulations. The continuous control strategy is then also implemented within a low-cost STM32-based control system, and both the swing and rotation stages of the brachiation motion are experimentally validated.

Single-Rod Brachiation Robot: Mechatronic Control Design and Validation of Prejump Phases

TL;DR

This paper addresses energy-efficient brachiation between bars using a minimal single-rod robot equipped with a crank-slide center-of-mass actuator. It develops two complementary control strategies: a bang-bang limit-case policy for rapid energy pumping and a practical continuous policy based on input-output linearization that respects actuator torque limits. A precise nonlinear two-degree-of-freedom model is derived from Lagrangian dynamics and used to analyze potential and Coriolis energy exchanges during swing and rotation, with a state-space form for simulation. The authors validate the methods in simulation with parameter identification and demonstrate experimental verification of the continuous policy on a hardware prototype featuring a STM32 controller, an IMU, and an encoder, achieving pre-jump brachiation between bars. The work lays groundwork for jump trajectory planning and hardware improvements aimed at higher efficiency and robust operation in inspection and maintenance tasks.

Abstract

A complete mechatronic design of a minimal configuration brachiation robot is presented. The robot consists of a single rigid rod with gripper mechanisms attached to both ends. The grippers are used to hang the robot on a horizontal bar on which it swings or rotates. The motion is imposed by repositioning the robot's center of mass, which is performed using a crank-slide mechanism. Based on a non-linear model, an optimal control strategy is proposed, for repositioning the center of mass in a bang-bang manner. Consequently, utilizing the concept of input-output linearization, a continuous control strategy is proposed that takes into account the limited torque of the crank-slide mechanism and its geometry. An increased attention is paid to energy accumulation towards the subsequent jump stage of the brachiation. These two strategies are validated and compared in simulations. The continuous control strategy is then also implemented within a low-cost STM32-based control system, and both the swing and rotation stages of the brachiation motion are experimentally validated.

Paper Structure

This paper contains 13 sections, 24 equations, 13 figures, 1 table.

Table of Contents

  1. Introduction
  2. Optimal motion of the center of mass
  3. Experimental Setup
  4. Dynamical Model of Single-Rod Robot
  5. State-space Description
  6. Control Policies
  7. Limit Case Control Policy
  8. Continuous Control Policy
  9. Case study validation
  10. Simulations of Limit Case Control
  11. Simulations of Continuous Control
  12. Experiments of Continuous Control
  13. Conclusions

Figures (13)

  • Figure 1: Phases of the robot's motion: 1 --- amplification of the swinging motion; 2 --- increasing of revolution speed; 3 --- preparation for release; 4 --- aerial phase
  • Figure 2: The general control policy for the first two phases of the robot's motion.
  • Figure 3: Mechanical design and main components of the single-rod brachiation robot
  • Figure 4: Block diagram of the experimental setup hardware components.
  • Figure 5: A scheme of the single-rod brachiation robot (crank-slide mechanism in side-view)
  • ...and 8 more figures