Previous Work in Automotive Systems

Adaptive Posicast Controller

Several automotive control problems require a control approach which can deliver a high performance in the presence of both uncertainties and large time-delays. Prime examples are Idle Speed Control (ISC) and Fuel-Air Ratio (FAR) control, both of which have been addressed with success through the use of adaptation. In ISC, the objective is to regulate the engine speed to a prescribed set-point in the presence of accessory load torque disturbances such as due to air conditioning and power steering. The objective in FAR control is to maintain the in-cylinder FAR at a prescribed set point, determined primarily by the state of the Three-Way Catalyst (TWC), so that the pollutants in the exhaust are removed with the highest efficiency. Adaptive Posicast Controller, an adaptive controller for time delay systems, has been used in these two control problems, and have led to a significant performance improvement.

Self-calibration in power-train systems with time-delay

Novel adaptive algorithms for Fully Adaptive Self-tuning (FAST) Controls in Powertrain Systems where time-delay plays a major role in performance optimization are being developed. FAST control strategies have the potential for reducing the calibration time and improving the performance in highly uncertain nonlinear dynamic systems. The concomitantly present hallmarks of ever increasing complexity and stringent performance targets in Powertrain systems, which become stronger and harder to achieve in the presence of time-delays, warrant the use of such adaptive algorithms. A unique methodology termed Adaptive Posicast Control has been developed in the lab, which has shown enormous improvement in gas turbine systems with large time-delays and have stringent performance specifications of safety and emissions. This Posicast control technology has been applied in Powertrain systems such as idle-speed control where time-delay plays a prominent role, where the expected impact is in the improvement of fuel economy.

Active-Adaptive Emission Control

Adaptive Shift Control

While driving, vehicle occupants notice when an inconsistent shift occurs. This not only degrades the user experience, but the fuel efficiency of the vehicle as well. In regards to powertrain control systems, inconsistent shifts contribute to a significant amount of "things gone wrong", as reported in consumer surveys. The biggest challenge for consistent shift control comes from a lack of feedback during the torque transfer phase in the presence of nonlinear and varying clutch dynamic response. As a result of this variability and absence of appropriate feedback, current shift control methods do not use actuator models and depend on shaft speed signals for feedback during the inertia transfer phase of the shift. This leads to a mostly open-loop control with limited disturbance rejection and non-robust performance, in particular, during the torque transfer phase. Adaptation is possible only based on previous shift events, thus allowing the occasional non-smooth shift. The objective is to design an enhanced adaptive control during shift, enabled by measurements of the shaft torque. Understanding of the clutch actuator dynamics and deriving suitable clutch models with adaptive parameters for control are the first set of steps of this effort.

Shift Hydraulic System

We are currently developing a model of the clutch actuation dynamics in a 6-speed automatic transmission similar to the experimental characteristics in the figure above [1]. The important dynamics we are considering are approximately between 3 and 4 seconds, which are highly nonlinear. [1] S. Watechagit. Modeling and Estimation for Stepped Automatic Transmission with Clutch-to-Clutch Shift Technology. PhD thesis, The Ohio State University, 2004.