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

摘要

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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> , v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> , and ω toward angular velocity each wheels of ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , ω <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> and v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> 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.