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Abstract



Modeling and Control of Electromechanical Actuators for Heavy Vehicle Applications


The possibility to develop control systems for electromechanical actuators at Scania is studied, in particular the focus is on how to exchange the intelligent actuators used today with dumb ones. An intelligent actuator contains its own control electronics and computational power, bought as a unit from suppliers by Scania and controlled via the CAN bus. A dumb actuator contains no means of controlling itself and its I/O is the motor’s power pins. Intelligent actuators tend to have limited control performance, time delays and poor diagnose systems, along with durability issues. A dumb actuator could have the benefit of avoiding these disadvantages if the system is designed within the company. A literature study concerning the different types of electrical motors available and their control methods is performed, the most suitable for use in a heavy vehicle is deemed the brushless DC motor, BLDC. An intelligent throttle is chosen for a case study and has its control electronics stripped and replaced with new sensor- and control cards. The case study is used to investigate the possibilities and difficulties of this design process. A simulation model is developed for the electronics, motor and the attached mechanical system. With the aid of this model a controller architecture is designed, consisting of PI controllers with feed-forward and torque compensation for non-linearities. The developed controller architecture is tested and in theory it can compete with the intelligent throttle’s performance. The model is also adapted to allow for code generation. The simulation model is used to study some common electrical faults that can effect the system and the possibilities for diagnosis and fault-remedial actions. The hardware prototype system shows that a current controller is necessary in the control architecture to achieve decent performance and the prototype is developed in such a way as to make future studies possible. The conclusion of the thesis is that Scania would be able to design control systems for dumb actuators, at least from a technical perspective. However more studies, from an economical point of view, will be necessary.

Alexander Pettersson and Patrik Storm

2012

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