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TECHNICAL BRIEFS

Bond Graph Based Approach to Passive Teleoperation of a Hydraulic Backhoe

[+] Author and Article Information
Kailash Krishnaswamy

 Honeywell Labs, 3660 Technology Dr., Minneapolis, MN 55418kailash.kvishnaswamy@honeywell.com

Perry Y. Li

Department of Mechanical Engineering, University of Minnesota, 111 Church St. SE, Minneapolis, MN 55455pli@me.umn.edu

J. Dyn. Sys., Meas., Control 128(1), 176-185 (Nov 19, 2005) (10 pages) doi:10.1115/1.2168475 History: Received March 15, 2005; Revised November 19, 2005

Human operated, hydraulic actuated machines are widely used in many high-power applications. Improving productivity, safety and task quality (e.g., haptic feedback in a teleoperated scenario) has been the focus of past research. For robotic systems that interact with the physical environments, passivity is a useful property for ensuring safety and interaction stability. While passivity is a well utilized concept in electromechanical robotic systems, investigation of electrohydraulic control systems that enforce this passivity property are rare. This paper proposes and experimentally demonstrates a teleoperation control algorithm that renders a hydraulic backhoe/force feedback joystick system as a two-port, coordinated, passive machine. By fully accounting for the fluid compressibility, inertia dynamics and nonlinearity, coordination performance is much improved over a previous scheme in which the coordination control approximates the hydraulic system by its kinematic behavior. This is accomplished by a novel bond graph based three step design methodology: (1) energetically invariant transformation of the system into a pair of “shape” and “locked” subsystems; (2) inversion of the shape system bond graph to derive the coordination control law; (3) use of the locked system bond graph to derive an appropriate control law to achieve a target locked system dynamics while ensuring the passivity property of the coordinated system. The proposed passive control law has been experimentally verified for its bilateral energy transfer ability and performance enhancements.

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Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Teleoperated backhoe consists of a motorized joystick, and a 2-DOF hydraulic backhoe actuated by a set of hydraulic cylinders and proportional valves

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Figure 2

Single-stage “passive valve” connected to a single-rod actuator

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Figure 3

Bond graph of the teleoperator after energy invariant coordinate transformation

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Figure 4

Bond graph of the master and slave systems with the coordination control law Eq. 19. Here EF1=−ρTE−ρ(KEE+BEĖ)−CLEĖ−Ψ−TCELq̇L.

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Figure 5

The fourth order desired locked system in Eq. 21

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Figure 6

Second order desired locked system

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Figure 7

Displacement trajectories (scaled joystick-solid, backhoe-dashed) during a digging task

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Figure 8

Haptic torque (Fq) trajectories (stick-solid, bucket-dashed) during a digging task

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Figure 9

Link 1 and link 2 displacement trajectories for fourth order locked system (joystick-solid, backhoe-dashed) during a digging task

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Figure 10

Locked system Force (ρTq−Fe) trajectories during a digging task for fourth order locked system (stick-solid, backhoe-dashed)

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Figure 11

Link 1 and link 2 displacement trajectories for the second order locked system (joystick-solid, backhoe-dashed) during a digging task

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Figure 12

Locked system force (ρTq−Fe) trajectories during a digging task for second order locked system (stick-solid, backhoe-dashed)

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