Ground Robotics Reliability Center

Andrew Niedert, Yazan Aljeroudi, Dr. Nassif Rayess, and Dr. Richard Hill

Department of Mechanical Engineering, University of Detroit Mercy

 

Design and Implementation of an Omni-directional Robotic Ground Vehicle

The purpose of this project is to validate a novel robotic ground vehicle design that has high-speed capability, omni-directional mobility and modest off-road capabilities. These goals will be achieved through the construction of the mechanical platform for the vehicle, as well as through the implementation of a control system that will assist a human driver in the teleoperation of the vehicle.

Purpose

Active Offset Split Castor (ASOC) Design Fully Independent suspension Ability to maintain traction of all six wheels Each DC wheel motor is independently controlled Motor motion is measured by Hall-effect sensors Pod rotation is measure by optical encoders

The vehicle in its current configuration

Overall Mechanical Design

Catia rendering of the designed vehicle

Conventional wheels

Hinge joint

Offset S

Split D

Vehicle Chassis

Conventional wheels

Hinge joint

Offset S

Split D

Vehicle Chassis

Each pod, and in turn the vehicle, is steered by differentially commanding the speed/torque of individual wheels Vehicle can strafe in any direction, rotate about its center, or drive like a conventional vehicle Can lead with two pods for stability or one pod for agility Slip rings allow for 360 degree pod motion while maintaining an electrical connection between the vehicle batteries, computer and data acquisition devices and the individual wheel motors and controllers

Top View: Active Spit Castor (ASOC) Design

Assembled pod

The Vehicle

Pod Design

ControlSoftware

Vehicle control software is implemented in the LabVIEW program from National Instruments running on a laptop on-board the vehicle LabVIEW allows for data acquisition as well as user inputs and actuator commands Software can interpret wireless commands from a PDA or video game controller Open-loop control is currently achieved using an inverse kinematic vehicle model Closed-loop control of vehicle heading is currently being developed employing an inertial measuring unit; a heuristic stability control algorithm is also to be developed

LabVIEW Front PanelVehicle Information GUI

LabVIEW Back PanelMotor input commands and data acquisition

Motor controller(Accepts signals sent by the DAQ assistant)

Data Acquisition CardSends and receives signals from hardware

Wireless GamePad ControlXbox 360 controller (top side controls)

Vehicle Characterization and Simulation

Vehicle characterization has been performed for the purposes of developing a dynamic simulation of the vehicle and a more advanced closed-loop control strategy Dynamics of the motors and their controllers have been approximated as 1st and 2nd order models Vehicle and component inertias have been identified using a scale and multi-filar suspension setup A simple longitudinal simulation of the vehicle has been implemented in Simulink The characterization of the wheel/road interaction is being empirically determinedA multi-body model of the vehicle will be interfaced with the current simulation in order to simulate lateral motion; this model will be implemented using the SimMechanics toolbox or using WorkingModel 2DThis simulation will be used to develop a closed-loop control strategy and to test different vehicle architectures

Acknowledgments

MicroStrain 3DM-G25Inertial Sensing Device

Simplified longitudinal vehicle simulation in SIMULINK

This work was funded in part by:The University of Detroit Mercy Faculty Grant Incentive Program, and