Simulation of road vehicle on engine test bed

The objective of this paper is to simulate road loads experienced by an automobile during an urban driving cycle on an engine test bed. This is to be achieved through the use of a combined eddy-current dynamometer and flywheel arrangement, to load the IC engine on the test bed, and an automatic throttle control system, which will vary engine power under changing load conditions to obtain the desired speed-time variation. This paper is intended to provide a system which will permit engine testing under realistically simulated urban driving conditions; it seeks to avoid the use of chassis dynamometers for this purpose. The test is conducted on the IC engine/dynamometer set-up, which consists of the Maruti Omini's 3-cylinder, 796cc, 37bhp (95000 rpm) petrol engine with drive train coupled with an eddy current dynamometer. The paper consists of the following stages 1. A driving cycle is defined, corresponding to urban driving conditions and tractive resistances are calculated and provided in the form of a resisting torque applied by the dynamometer on the IC engine, controlled by a rnicrocontroller. 2. Inertial loads are calculated and applied on the IC engine via both the dynamometer and a flywheel, which is attached to the dynamometer mounted on a separately fabricated assembly. 3. Throttle control is achieved using a stepper motor, which is used to modify the existing manual throttle control setup. The stepper motor is operated using a micro controller. An interfacing circuit has been fabricated to allow this and program written is used to control the stepper motor and provide desired throttle positions through the driving cycle. 4. Torque control in the dynamometer is to be achieved by using the 'external mode' available on the control panel of the dynamometer. This allows communication of values from a micro controller via a parallel port, digital-analog converter, and driver circuit, in the form of voltages signals, allowing torque control to be achieved.