Experimental results of a high speed robotic autoloader for a howitzer

The dynamics of robots are characterized as multi-degree-of-freedom and nonlinear. Relatively few control algorithms have been implemented in real-time applications where one must consider: unmodelled dynamics, robustness, noise, stiction, backlash, actuator nonlinearity, saturation, time varying effects, power usage, computational requirements, and development cost. This paper describes the experimental results of a nonlinear control algorithm (inverse dynamics feedforward with feedback compensation) that was implemented in a high speed robotic system to see how the controller dealt with those issues. The controller was used in an electric autoloader (robot) for the Army´s M109 155 mm self propelled howitzer. The function of the autoloader was to retrieve projectiles and propellant from a storage magazine and load them into the gun at a high rate. In this application, control of the autoloader was complicated by the large masses that had to be actuated from one place to another in a very short time (less than 1 second) to fire 4 rounds in 20 seconds. This paper also describes the technical considerations in developing the robotic autoloader to achieve high speed and accuracy, the manipulator control system, and the special hardware that was built to handle the computational and electrical power requirements