MOTION CONTROL OF A PROPEL CIRCUIT TESTBED FOR THE HYBRID HYDRAULIC ELECTRIC ARCHITECTURE (HHEA)

Current off-road hydraulic machines are highly inefficient. Research is ongoing to develop a fully electrified compact track loader based on the Hybrid Hydraulic Electric Architecture (HHEA), to gain the benefits of electrification without needing large electric machines. The HHEA is being applied to both the work and propel circuits. This paper focuses on developing the propel motion control system using HHEA. The main challenge in developing a motion control system for the HHEA is the abrupt disturbance due to frequent switching between discrete pressure rails as loads vary. Pressure rail switching is inherent in the HHEA system for energy saving and downsizing the electrical components. Similar to a previously proposed control system for the work circuit, the control system for the propel circuit testbed also combines a nominal controller for speed regulation and a transition controller to compensate during rail switching events. A nominal controller is designed as a pole-placement controller, and a transition controller consists of a disturbance feedforward controller. The speed control performance on the testbed was experimentally evaluated for various torque and rail switching options. The experimental results demonstrate that the proposed control strategy precisely controls the propel shaft speed, which validates this architecture potential to improve efficiency without compromising performance.