Wheel Configuration

Most mice roll on wheels. Deciding on the layout of the wheels will affect the performance of the mouse and will determine how easy it is to control. The three most popular configurations are:

Wheelchair

This design uses two wheels, one on either side of the mouse. Each of these wheels is then driven independently by its own motor. By slowing down or reversing one of the motors, the robot is able to steer. Balance is achieved by placing casters or sliders at the front and back of the chassis. This design is easy to construct and, if the chassis is small enough, the mouse can rotate in place.

Tricycle

The tricycle design is similar to the wheelchair design. Instead of having a passive castor as the balancing point, however, you have a third wheel out front which is steered with a servo motor. The problem with the wheelchair design is that any discrepancies in the wheels, the motors or the control system will cause the mouse to travel in a slight arc instead of a straight line. The tricycle configuration tries to overcome any slight errors and force the mouse to go straight. Tricycle designs, however, tend to be larger than the wheelchair design and turning around within the confines of a cell usually involves a 3-point turn.

Four wheel mouse

This is a very stable design for high-speed mice but it is difficult to achieve unless the designer is good in the machine shop. Each of the four wheels has its own drive motor and there are at least 2 more motors to steer the wheels. These designs do not attempt to turn around but rather have sensors on both ends of the mouse. When it encounters a dead-end it simply starts traveling in reverse.

 

Finding Wheels

One of the problems that first time MicroMouse builders are confronted with is finding suitable wheels. If you don't have access to a machine shop, consider removing the wheels from a toy car (that's what we did for Dexter). Another source of wheels are hobby shops. Look at wheels intended for remote controlled cars and airplanes. You might have to modify them to get them to fit. Finally, with the success of small robots as a hobby, there are several companies that will sell you wheels which are made to be attached to servo motors.