The wheel robots are for the larger part derived from the Mars rovers, which have actuators integrated into the wheels to help with the movement on the rugged grounds in space. This is made possible with the help of 12 volt linear actuators.
There is some elemental aspects of robotics that are involved in the setup. For there to be synchronous movement on a ground that is not evenly leveled, there is need for each of the units to have its own local control unit.
The local control units are then connected to the central control unit to make sure that they all are moving in the same direction, despite the fact that the wheels they control are experiencing variance in travel and elevation.
To enhance the level of control, there are in-wheel steering mechanisms along with in-hub traction motors. The steering system is able to achieve 95–25% degrees. Given these angles, the robots are able to rotate on their own vertical axis and even move sideways.
Ideally, there is the element that is crucial, when the robot needs to turn at a point or move on its side to avoid obstacles that are on its path. It is possible to decouple the wheels and control them independently. This is a common aspect on the ROboMObil.
The ROboMObil are designed on the module concept, with a composite of four modules. There are two axles on the front and at the rear, and an additional body module. The body module is crucial relative to the fact that is houses the vehicle body sensors, onboard computer systems along with the driver compartment. Below the body module is the high voltage battery back.
Within the wheel architecture is the permanent magnet synchronous motor. This is a magnet that allows the wheels to be steered within the extended angles highlighted above. Additionally the traction motors provide the vehicle with velocities of up to 100km/h and a peak torque of about 160Nm, for each of the wheel.
To assist with steering within the motor housing, each of the wheels has an electric rotary actuator. Compared to the steering actuation that is provided for by the tie rods in most of the vehicles, this system offers a wide range of motion. This is a process that largely assisted by the permanent magnet synchronous motor, which is connected to the backlash free harmonic drive transmission.
The electric motor housing provides a place to mount the rotary actuator that is used on each of the wheels for steering. The braking on the other hand uses friction brakes that are electrohydraulic actuated. However there are developments that look to optimize the aspect of cooperative braking between the friction brakes and the traction motors.
The ROboMObil uses the double wishbone geometry relative to the fact that it offers geometric properties and that it is possible to get an outboard actuator for the steering system. The ROboMObil uses electro-rheological dampers, which are adapted for their effectiveness relative to the wide range of motion on the wheels.
It is also crucial to elements of making sure that the vehicle does not compromise between road holding grip and the ride comfort. The wheel robot can be quite challenging given that wheel are quite large in light of the in-wheel traction motors along with the steering actuator.