| Planetary rover is a mobile robot used to explore complex environment of planet.The research of planetary rover involves mechanics, computer technology, Automaticcontrol and other disciplines. Control system is the basis and the key of the planetaryrover. The performance, stability and reliability of the control system can directlyinfluence the success of a deep space exploration mission.In order to discuss the traction control system of planetary rover, the motionmechanism, data communication methods and driving system of the four-wheelplanetary rover are designed. The planetary rover prototype can be used for theexperiment test of several navigation algorithms.Through analysis and comparison of mechanical structure, kinematics characterof planetary rover at home and abroad, four-wheel rocker-bogie structure is adopted tobuild the planetary rover entity model. Four-wheel planetary rover mobile subsystemis composed of vehicle wheel, suspension system, connection device betweensuspension system and rover body and steering mechanism. The suspension system iscomposed of rocker and hinge structure. The planetary rover can complete thefunctions of forward, backward and turn at an arbitrary radius. This structure ofplanetary rover can share the body load evenly on each wheel and has strong adapt-ability for the ground and the ability of obstacle surmounting.The data communication system of planetary rover is responsible forcommunications between subsystems of planetary rover. A distributed multi-axisdriving system based on CAN bus under VxWorks operation system is designed atthis topic. High-performance motor controllers and encoders with CANopen interfaceare chosen as CAN bus nodes in the driving system. The higher layer protocolCANopen based on CAN Bus is developed. Motor controller command instruction setis compiled. The driver of MSMCAN PC104board card is configured.8motors aredriven independently in the CAN bus communication mode and speed correspondingcontrol of planetary rover is completed. Absolute magnetic encoder is designed tomeet planetary rover functional requirements and wheel angle information is collected.The speed corresponding control of four-wheel planetary rover is proven to meetbasic independent drive needs.Forward kinematics and inverse kinematics model of four-wheel planetary rover under the condition of slip is made with the industrial robot method of D-H at thistopic. This kinematics model can characterize position and orientation of planetaryrover in rugged terrains and the velocity relationship between rover body and wheel.The research establishes the theoretical basis for motion control of four-wheelplanetary rover. The open-loop kinematics calculation method is test on the dynamicsimulation platform. The experiments suggest that by using traction control methodbased on the inverse kinematics the planetary rover can achieve good effect. |
