Andrew Niedert , Richard Hill, and Nassif Rayess

1
Modeling, Simulation, and Control of an Omni-directional Robotic Ground Vehicle Andrew Niedert, Richard Hill, and Nassif Rayess University of Detroit Mercy, Department of Mechanical Engineering • Control algorithm is needed to translate vehicle-level commands from driver (V x , V y , ω) into commands to the six individual motors • Driver commands are input via a video game console that wirelessly transmits the information to a laptop on board the vehicle running LabVIEW software Dynamic control scheme • Necessary to assist driver in maintaining vehicle heading in the presence of disturbances and model uncertainties • Calculations are done in a body-fixed frame to remove need for an inertial sensor • Control scheme includes a kinematics-based feedforward term and a dynamic PID feedback term that closes the loop on pod angle This work sought to test the feasibility of a novel vehicle architecture and to develop a dynamic multi-body simulation tool to assist in the development of future iterations of such a vehicle. The vehicle design aimed to achieve high-speed capability, omni-directional mobility, and modest off-road capability via tele- operation. 4 th Annual IEEE International Conference on Technologies for Practical Robot Applications (TePRA2012) April 23-24, 2012 Boston, Massachusetts Control Algorithm and Software Abstract The Vehicle • Each of three pods, and in turn the vehicle, is steered by differentially commanding the speed of two individual wheels • Three pods provides control authority in rough terrain • Vehicle can strafe in any direction, rotate about its center, or drive like a conventional vehicle • Slip rings allow for 360-degree pod motion relative to the vehicle chassis while maintaining an electrical connection Multi-Body Dynamic Simulation Planar dynamic simulation of multi- body vehicle (chassis and three pods) implemented in SimMechanics addition to Simulink, includes animation • Simulation model includes characterization of the road/tire forces (longitudinal and lateral) [2], drag force, closed-loop motor dynamics, and vehicle inertias Assembled pod The vehicle in its current configuration Conventional wheels Hingejoint O ffset S Split D VehicleChassis Conventional wheels Hingejoint O ffset S Split D VehicleChassis Top View: Active Spit Offset Castor (ASOC) Design · Active Split Offset Castor (ASOC) modules [1] achieve omni- directional mobility with reduced scrubbing · Fully independent suspension maintains road contact · Each DC wheel motor is independently controlled · Motor motion is measured by Hall- effect sensors · Pod rotation is Pod Design Experimental and Simulation Data Vehicle is challenging to drive with slip- ring friction, easy without • Simulation provides good qualitative agreement with physical data Vehicle velocity data under straight-line motion S-course employed for vehicle testing Vehicle heading data during traversal of S-course Vehicle simulation as implemented in SimMechanics LabVIEW Back Panel Motor input commands and data acquisition Wireless GamePad Control Xbox 360 controller (top side controls) [1] Yu, H., Dubowsky, S., and Skwersky, A., 2004. “Omni-directional mobility using active split offset castors.” Journal of Mechanical Design, 126(5). [2] Pacejka, H., and Bakker, E., 1992. “The magic tyre formula model.” Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility, 21(1). References

description

Andrew Niedert , Richard Hill, and Nassif Rayess University of Detroit Mercy, Department of Mechanical Engineering. Control Algorithm and Software . Abstract. Multi-Body Dynamic Simulation . - PowerPoint PPT Presentation

Transcript of Andrew Niedert , Richard Hill, and Nassif Rayess

Page 1: Andrew Niedert , Richard Hill, and  Nassif Rayess

Modeling, Simulation, and Control of an Omni-directional Robotic Ground Vehicle

Andrew Niedert, Richard Hill, and Nassif RayessUniversity of Detroit Mercy, Department of Mechanical Engineering

• Control algorithm is needed to translate vehicle-level commands from driver (Vx, Vy, ω) into commands to the six individual motors

• Driver commands are input via a video game console that wirelessly transmits the information to a laptop on board the vehicle running LabVIEW software

Dynamic control scheme• Necessary to assist driver in maintaining vehicle heading

in the presence of disturbances and model uncertainties• Calculations are done in a body-fixed frame to remove

need for an inertial sensor• Control scheme includes a kinematics-based feedforward

term and a dynamic PID feedback term that closes the loop on pod angle

This work sought to test the feasibility of a novel vehicle architecture and to develop a dynamic multi-body simulation tool to assist in the development of future iterations of such a vehicle. The vehicle design aimed to achieve high-speed capability, omni-directional mobility, and modest off-road capability via tele-operation.

4th Annual IEEE International Conference on Technologies for Practical Robot Applications (TePRA2012)April 23-24, 2012 Boston, Massachusetts

Control Algorithm and Software Abstract

The Vehicle

• Each of three pods, and in turn the vehicle, is steered by differentially commanding the speed of two individual wheels• Three pods provides control authority in rough terrain• Vehicle can strafe in any direction, rotate about its center, or drive like a conventional vehicle• Slip rings allow for 360-degree pod motion relative to the vehicle chassis while maintaining an electrical connection

Multi-Body Dynamic Simulation • Planar dynamic simulation of multi-body vehicle (chassis and three pods) implemented in SimMechanics addition to Simulink, includes animation • Simulation model includes characterization of the road/tire forces (longitudinal and lateral) [2], drag force, closed-loop motor dynamics, and vehicle inertias

Assembled podThe vehicle in its current configuration

Conventional wheels

Hinge joint

Offset S

Split D

Vehicle Chassis

Conventional wheels

Hinge joint

Offset S

Split D

Vehicle Chassis

Top View: Active Spit Offset Castor (ASOC) Design

· Active Split Offset Castor (ASOC) modules [1] achieve omni-directional mobility with reduced scrubbing· Fully independent suspension maintains road contact· Each DC wheel motor is independently controlled· Motor motion is measured by Hall-effect sensors· Pod rotation is measured by optical encoders

Pod Design

Experimental and Simulation Data

• Vehicle is challenging to drive with slip-ring friction, easy without• Simulation provides good qualitative agreement with physical data

Vehicle velocity data under straight-line motion

S-course employed for vehicle testing Vehicle heading data during traversal of S-course

Vehicle simulation as implemented in SimMechanics

LabVIEW Back PanelMotor input commands and data acquisition

Wireless GamePad ControlXbox 360 controller (top side controls)

[1] Yu, H., Dubowsky, S., and Skwersky, A., 2004. “Omni-directional mobility using active split offset castors.” Journal of Mechanical Design, 126(5).

[2] Pacejka, H., and Bakker, E., 1992. “The magic tyre formula model.” Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility, 21(1).

References