Inverse kinematic implementation of four-wheels mecanum drive mobile robot using stepper motors

An implementation of inverse kinematic model is applied for the mobile robot using four-wheels mecanum drive. The implementation is designed for omni-directional movement without changes the robot position on a facing direction. Four stepper motors are used to drive the mecanum wheels due to these types have a good precision. This speed control feedback is not necessary. The radius of the mobile robot dimension is defined by the same distance of a and b length between wheel axis and body center of 170 mm. The inverse kinematic is conducted to control the mobile robot movement and to convert the robot velocity component of v_x, v_y, and ω toward angular velocity each wheels of ω₁, ω₂, ω₃, ω₄ and wheel turn direction. Kinematic calculation and control mechanism are proceed by a master microcontroller and multi-slave microcontrollers which connected using SPI communication protocol. The theta angle θ is described by v_x and v_y vector velocity direction toward center point of the mobile robot. The movement capabilities are performed by linear direction according to the certain angle of the robot movement θ of 0° to each multiples of 45° thus obtained wheel velocity and angle movement average errors.