Generic Modeling and Control of an Open-Circuit Piston Pump—Part II: Control Strategies and Designs

Abstract

Hydromechanical compensators are often integrated with piston-type pumps to produce various control behavior, for example, pressure, load-sensing, power, or torque control. Various hydromechanical mechanisms (e.g., spring forces and load pressure) are found in the industry to ensure the desired effect of the system outputs: swash angle, discharge pressure, and input torque following the reference inputs. In a companion paper (Part I of this paper), a generic linearized state-space model is derived to investigate the pump dynamics and determine the design criteria and parameters. In the study, the state-space equations are used to propose and define the generic compensating control pump to conduct the similar strategies as hydromechanical pumps do. The different control purposes (pressure/flow/power compensating) are accomplished by only manipulating the generic regulate inputs given by an electrical proportional control valve. In the open-circuit pump, the generic controllers are proposed to generate these inputs by using one unique mechanical and electronic architecture to establish various purposes of flow, pressure, torque desired control, and even more control objectives. The controller is developed in accordance with the state-space representation and by following the models of the hydromechanical compensators that can facilitate the correlation verification. The proposed controllers are able to offer more intelligent and cost-saving control strategies for open-circuit piston pumps. To achieve the similar performance as hydromechanical compensators do and implement the comparative study, control gains and settings in the controller can be determined from ones that hydromechanical compensators have. The difference is that electronic signals (swash plate position, pressure, etc.) work as feedbacks together with other control gains to regulate the input signals. For the different control purposes, control gains are able to be set conveniently for the various control operating conditions with combining the certain feedbacks on the same hardware platform that will be value efficient and capable of control intelligence. In the paper, results of predictions made by the model are presented and compared with some experimental data of hydromechanical designs. Further work on the advanced model-based control and estimation is anticipated to be addressed.