Research Of Omnidirectional Mobile Robot Based On Mecanum Wheel

Mecanum wheel is an omnidirectional mobile mechanism that has excellent performance and iswidely used, so the omnidirectional mobile robot equipped with this wheel can easily achieve3-DOFmovement in the plane. It can successfully complete complex tasks like transportation, assembly,detection, nuclear operation in the fields that require precise positioning and high-precisionnavigation.As a typical nonholonomic constraint system, the mobile robot based on Mecanum wheel isdominated and affected by the ground conditions when moving. The rollers of Mecanum wheelcontact with the ground in higher pair, thus the contact stress is so big that deformation and weargenerated in the process can’t be ignored when talking about motion accuracy and carrying capacityof the robot. What’s more, slide of Mecanum wheel is a common phenomenon as a result of theexistence of axial force, the inhomogeneity of motor speed and the ground conditions. All of this havea serious impact on the stability of the robot. So a thorough understanding of the contactcharacteristics and the slide problem between the rollers and the ground are the prerequisites toimprove the motion accuracy and carrying capacity of the robot. On the basis of these, the paperincludes:1. The parameterized modeling method of theoretical roller generatrix and the definition of themain parameters of the wheel body are put forward. Then the internal structure of the roller and theselection of the outer material are illustrated.2. Contact analysis between the Mecanum wheel and the ground. At first, the contact model, theexternal forces and the space angles of rollers are explored. As a key section, it sets up the generalmodel of space contact problem using Hertz theory. Based on the model, the maximum stress anddeformation of contact are worked out, from which the cause of vibration is derived. Then, the brushmodel of Mecanum wheel is established to get the mechanical properties of contact area. Also, anumerical method for calculating the wear amount is presented. Afterwards, it sets up the contactmodel on the basis of two kinds of roller structures using ANSYS software, from which we get thedeformation, stress and strain distribution of the roller under different pressures. The results alsoverify the validity of Hertz theory in dealing with this problem. At last, we proposed the optimizationdesign methods of the roller contour. The results of the study are of great significance to improve themotion accuracy and the carrying capacity of the robot. 3. Modeling, simulation and slide control of the mobile robot. The general kinematics equationof the Mecanum wheeled mobile robot is obtained by vector analysis method, from which the forwardkinematics and the inverse kinematics of four wheels are derived. With the Lagrange equations, thedynamics model of four Mecanum wheeled robot is built. Afterwards, it deals with the ability ofMecanum wheeled mobile robot in realization of3-DOF movement with ADAMS, then it analyzesreasons of simulation error and puts forward a control method about the limitation of motor speed,which can reduce sliding phenomenon effectively. Finally, we explored the sliding model of fourMecanum wheeled platform, a PID controller based on SimMechanics model is established. Bysimulating sliding, the controller can effectively eliminate the position deviation caused by sliding.