Control for Electrical Coolant Valve in Engine Thermal Management Module

Paper #:
  • 2017-01-2204

  • 2017-10-08
Hyundai Motor Company recently developed a multi-way, electrical coolant valve for engine thermal management module. The main purposes of the system that replaces a mechanical thermostat are to boost fuel economy by accelerating warm-up and to enhance thermal efficiency by actively controlling engine operating temperature. The electrical valve controls the amount of coolant flow to components such as oil heat exchanger, heater core, and radiator, while providing separate cooling for engine block and head. The coolant flow is modulated by varying the valve angle actuated with an electric motor. The system operates under a thermal management strategy that consists of multiple phases including zero coolant flow mode, and for those phases that require coolant temperature control, a feedback algorithm is designed for the flow control. This paper discusses the control law of coolant control valve developed for an actual prototype vehicle and also provides the results acquired from actual vehicle tests. The main objective of the controller is to force engine outlet coolant temperature to follow the engine operating temperature target determined by engine operating conditions. The biggest challenge in this system is that there exists a significant amount of delay between valve actuator and the water temperature sensor that is located at the outlet side of the engine. In order to mitigate this problem, a cascade approach is taken. The outlet coolant temperature is indirectly controlled by regulating inlet side coolant temperature, which is easier to control due to relatively smaller amount of delay. The cascade logic consists of two feedback loops: a feedback controller to calculate an intermediate temperature target for inlet, based on the engine heat rejection data acquired from dyno tests and the error between outlet temperature and the target, and another feedback loop to force inlet coolant to track the calculated inlet target.
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