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The ARTSA-i Brake Calculator provides a calculation of the deceleration performance of four types of combination heavy vehicles:
The performance of the truck and the trailer separately can be studied by setting the brake performance of the other vehicle to zero.
Each vehicle can have different numbers o f axle in each groups within the limits provided. The user can alter the brake torque available at each wheel. Thereby the user can study the effect of altering the brake set-up. Provision is also provided to alter the air-valve characteristics.
The purpose of the calculator is to predict the likely braking performance when a (combination) vehicle is stopped with constant conditions from a nominated starting speed.
The calculator is applicable to prediction of Australian Design Rule 35 and 38 performances. It is also applicable to prediction of Performance Based Standards (PBS) Directional Control Under Braking standard.
The program includes a foundation brake model and a parking brake model. The model includes a discount factor for drum brake performance that attempts to model the effects of the brakes heating up during the stop. The model predicts wheel lock-up performance by recognising that a wheel cannot extract more retardation force from a road than is available from the tyre friction.
The user may use the calculator to predict the performance of Antilock Brake System by varying the parameters of the tyre lock-up model.
The primary output of the calculator is the vehicle deceleration that occurs for each of 20 brake control levels up to 650kPa (100%) brake control pressure. The stopping distance is predicted from the calculated deceleration level taking account of an assumed braking time delay.
The calculator has been developed by ARTSA-i with financial assistance from the Federal Heavy Vehicle Road Safety Initiative that is administered by the National Heavy Vehicle Regulator (NHVR).