Closed loop control over ISO 11783 network – challenges of plug-and-play

ISO 11783 is a communication standard for agricultural machines, especially to distribute information between a tractor and implements (agricultural tools) connected to that. The first goal in the standard is manufacturer independent communication, the second is to use the same operating terminal to control all the implements connected to a tractor and the third is related to precision farming and information systems. ISO 11783 standard provides three classification levels for a tractor manufacturer; in Class 1 tractor has to broadcast only the basic measurements to the network, in Class 2 more measurements and in Class 3 tractor is capable of handling requests or commands from implement. This most advanced level, Class 3, enables closed loop control over a network. The implement may command either level of tractor hitch, engage power takeoff, or control auxiliary hydraulic valves. With ISO 11783 Class 3 tractor, a closed loop control over a network can be designed. In the case, the controller resides on the implement while the actuators are in the tractor. The tuning of such a system can be made by hand, for one tractor and one implement. This paper discusses challenges related to implementing closed loop control over ISO 11783 network. The main question is that how the implement has to be designed in order to be compatible with any tractor. Means to tackle the problem are shortly: requesting physical parameters and the gain scheduling, automatic identification of tractor parameters and feasibility of adaptive control. The paper introduces a proposed initial test procedure to be done before closed loop control can be enabled. Nevertheless, the identification and adaptive control of a multi degree-of-freedom system with various unmeasured loads and common hydraulic system is found to be extremely challenging in case of any tractor and any environmental conditions.