Остання редакція: 2020-05-16
Анотація
Robots come in different varieties and shapes, but almost all of them have some features in common. That implies some mobile platform and an end-manipulator. The purpose is to move in wide range within an allowable space and to perform high-precision manipulations in the desired position for mobile platform and manipulator, respectively. Bearing in mind, that different terrains and conditions are suitable for different types of robotic platforms, as for example differential drive robot that has two independently controlled wheels and one or more to keep it planar; a regular car-like platform; a platform with omnidirectional or mecanum wheels that allow skidding in other direction than forward or backward; and tank-like robot with tracks.
Specifically, one group of car-like robots are the hardest to control in term of planning the trajectory. This is due to nonholonomic constraints to the configuration of the chassis – the car cannot move sideways directly, it can achieve net sideway displacement by “parallel parking” maneuvers, however.
The author for his project of mobile manipulator has chosen a platform with four mecanum wheels. This setup allows to move in any arbitrarily direction only by spinning the wheels in different directions and different speeds. In mathematical terms it is done by matrix transformation H(0) that maps some planar twist Vb to the angular speed of each particular wheel.