Specifying a hydraulic regenerative braking system for an articulated urban delivery vehicle
Previous research has shown that hydraulic systems offer potentially the lightest and smallest regenerative braking technology for heavy goods vehicles. This paper takes the most practical embodiment of a hydraulic system for an articulated urban delivery vehicle and investigates the best specification for the various components, based on a simulated stop-start cycle. The potential energy saving is quantified.
Vehicle dynamics control with energy recuperation based on control allocation for independent wheel motors and brake system
This work proposes an optimal control allocation method for the brake system and the wheel motors of an electric vehicle. The realisation of the method is proposed for vehicle dynamics control and energy recuperation. The control allocation takes into account temperature of electric motors, SOC and voltage of battery, vehicle velocity, fault situations, wheel slip, and vehicle subsystem prioritisation depending on parameters of vehicle dynamics. To illustrate the functional properties of the control allocation method, the corresponding simulation study is performed for the straight-line braking and ‘sine with dwell’ cornering. The simulations use a number of mathematical models including the 14 DoF model of vehicle motion and the models of electric vehicle systems. The simulation results confirmed effectiveness of the proposed approach both for regenerative braking and vehicle stability.
Validation of a power based model of car fuel consumption
A power based model of car fuel consumption has recently been proposed but the model validation was inadequate. This report describes the power model in detail, explores the areas of use of the model and documents a thorough investigation of the calibration procedure and prediction errors. Extensive dynamometer and on road data, including data from well controlled on road acceleration, deceleration and steady speed tests, were used in the validation task. The on road drag power was found to be best estimated by a two term function of speed (v and v**3) using coast down or steady speed fuel consumption data. The efficiency parameter of the power model was found to be dependent on the calibration data, and hence the choice of the data is very important. Model parameters should be estimated independently where possible using second by second speed and fuel consumption data. A procedure is outlined for parameter estimation when fuel consumption cannot be measured accurately in one second intervals. The power model was found to be suitable for use in the area of traffic management. It was found to be sufficiently accurate for predicting fuel consumption during trips and segments of trips of 60 s duration or more, and for predicting steady speed and acceleration fuel consumption (except very hard acceleration). The errors were generally less than 10 per cent for these applications. Extensions to the power model reduced the prediction errors during decelerations and hard accelerations but had little affect on the general predictive capabilities of the power model (a).