This approach was originally developed by Borenstein and Koren [6] for a two-wheel differential drive vehicle; it was later refined and applied to a four-wheel drive skid-steer robot to improve odometry accuracy [7].In this paper, the CCC idea is implemented and experimentally validated for the general case of a rover outfitted with four independently steered and driven wheels. The system continuously compares the actual encoder readings from all four wheels and issues corrective commands to the motors to slow down the motors that are faster and speed up the motors that are slower than the others. In conventional mobile robots controllers, each drive loop receives no information about the others, and any disturbance in one loop causes an error that is corrected only by this loop, while the other loops carry on as before.

Cross-coupled control is used to remedy this problem by sharing the feedback information of all control loops. The overall effect is that the wheel velocities are matched more tightly even in the presence of internal and external disturbances. It should be also noted that the proposed control strategy does not require any additional sensors other than wheel encoders and steer potentiometers that are commonly available in most robots.A cross-coupled LQR-based controller was proposed and demonstrated via simulations for a four-wheel robot in [8], aiming to drive and steer all the wheels at their respective required angles keeping the corresponding errors mutually proportional.

Behavior-based approaches were also used to solve Batimastat the actuators’ coordination problem in four-wheel-steering robots [9,10].

Specifically in [10], the authors proposed a steering controller where virtual linkages are created between each wheel to maintain Brefeldin_A the correct kinematic constraint and minimize wheel slip. An alternative solution for the wheel synchronization problem was proposed in [11], who used a voting scheme to synchronize the six wheels of JPLs FIDO Mars Rover.The proposed CCC algorithm is validated in the field using the all-terrain rover Dune, built at the Applied Mechanics Laboratory of the University of Salento. Dune, shown in Figure 1, is an independently controlled four-wheel-drive/four-wheel steer mobile robot, also featuring a rocker-type suspension system. This architecture provides a high degree of mobility, allowing the robot to safely traverse rocks over one and half its wheel diameter and to perform special maneuvers such as crab and turn-on the spot motion. Its operational speed ranges from 2 to 40 cm/s.