Abstract
This paper describes how Electro Mechanical Brakes (EMB) can be integrated in a Brake by Wire (BbW) system architecture on heavy vehicles and the improvements being achieved regarding brake function performance and energy savings.
By replacing the existing brake system structure on heavy vehicles, which is based upon compressed air as energy source, with a fully BbW system a significant improvement in braking performance and thereby vehicle safety will be achieved. The brake torque on each wheel-end can be individually monitored in a very accurate way which allows a better utilization of the existing tire/road friction conditions. In particular in emergency brake situations and during traction control on low friction conditions significant improvement can be achieved compare to a pneumatic brake system of today. Result of vehicle tests has shown a shortage of the braking distance in emergency brake situations by 15 % in average on different road conditions. This result comes very close to what is physical possible to achieve from a brake system in terms of performance. During normal braking applications the quick response time of an EMB System gives the driver a much better pedal feeling and a more precise control of the vehicle in general.
From the complete vehicle combination ( Truck/Trailer ) perspective control functions like brake blending and trailer coupling force control will be improved concerning driver comfort, brake balancing and brake pad wear when equipped with an EMB system. The combination of Model based design of the control functions and actuators ( EMB ) with very predictable characteristics gives a good alignment between simulations and the performance on the test track. In order to reduce the external power demand to perform a brake application the brake mechanism design is based upon the principle of self enforcement, using the rotational energy from the wheel to create clamp force between pad and disc. This enables to continue using a 24 V power supply system also for future BbW systems. The long term trend of growing road transportation and higher traffic density will require systems with increased vehicle/road safety and are more energy efficient in operation. A brake system with EMB technology will contribute very well to those demands.
Keywords: Brake by Wire, Electro Mechanical Brake, Energy Consumption, Slip Control, Brake Performance