Design and nonlinear force control of a power-by-wire piezoelectric-hydraulic pump actuator for automotive transmissions.

摘要

In this dissertation research, a new concept of actuation system and corresponding control method are developed for automotive automatic transmission (in short, AT) shift control.;A piezoelectric-hydraulic pump (in short, PHP) based actuation system can be one of the potential alternatives that can replace a current electro-hydraulic actuation system for an automatic transmission friction element such as a band brake. In this dissertation, a stand-alone prototype of the PHP actuator is synthesized with the new concept of power-by-wire actuation, with a primary emphasis on the development of required performance for AT shift control. The fundamental performance of a prototype PHP is evaluated through the measuring of the flow rate and dead-head pressures. In addition, both the effects of a Helmholtz resonator and a fluid effective bulk modulus on the performance are experimentally examined.;Next, a nonlinear sliding mode controller is developed for actuation force tracking control of the piezoelectric-hydraulic pump based actuation system. With a derived governing equation of motion of the PHP-band brake actuation system, a simple but effective switching control law is synthesized based on the sliding mode theory for the given nonlinear system. To demonstrate the effectiveness of the proposed controller, its force tracking performance for a smooth engaging of friction elements during the AT 1 → 2 up shift is validated experimentally. In addition, implementation method using a two-level driver that is appropriate for a pulse-driven actuator is established. It not only can successfully track the desired force trajectory for AT shift control with small tracking error, but also provides a new opportunity for pressure control of fluid power systems, eliminating three traditional hydraulic components: oil pump, regulating valve, and control valve. These promising results demonstrate the potential of the PHP actuator as a new controllable actuation system for AT friction elements.;Finally, the PHP actuator and controller are applied to the automatic transmission shift control scenario to examine the effectiveness of the new power-by-wire actuation concept. To do this, a real time automotive power train model is first synthesized to develop the simulation model for hardware-in-the-loop simulation. Only power on 1 → 2 up shift model using band brake as on-coming friction element and one-way clutch as off-going friction element is provided for evaluating the single actuator performances. In addition, both fill volume control to prevent over-fill and the desired force trajectory learning control for AT shift controller are designed to achieve the enhanced shift performance. With the real time power train model and the PHP actuator, the whole structure of HILS is constructed, and its successful use in the development of AT shift control system is presented to demonstrate the feasibility and benefits of using the new PHP actuator.