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Since more than eight years Vienna Engineering (VE) is working on an electro-mechanical brake (EMB) actuated by eccentrics and a highly non-linear actuation mechanism. The principle allows full braking in approx. 70 milliseconds (including air gap) and only approx. 3 A RMS actuator current at 12 V for classical ABS with oscillations. This EMB reached an elaborated state. Versions for passenger cars, elevators, railway and commercial vehicles (CVs) were derived. Now, as the EMB is going to road tests, it is necessary to fulfill safety requirements closely. What are these safety requirements and how can they be fulfilled? The properties of the overall system, of the mechanics and electronics of the single brake are discussed in this paper. The overall brake system for EMBs needs a truly redundant power supply, a safe control bus and a safe brake pedal. The mechanics of a single brake can be required to release when power is off and it must not get mechanically stuck.

At first glance a friction brake should be controlled by normal force to produce predictable brake force. Controlling an actuator (and hence brake pad) position basically seems to introduce uncertainties to normal force and brake force, because at first view the position tells little about actual normal force. The electro-mechanical brake (EMB) of Vienna Engineering (VE) can be operated by position-control, either without force sensor (saving costs) or even with a true brake torque sensor. For position control a relation between actuator position and normal force is used. When pad wear is correctly adjusted a certain actuator position produces a given deformation and at known elasticity the deformation produces a defined normal force. In the VE-EMB this relation uses a three-dimensional curve and includes temperature influence of the coefficient of friction, thermal expansion and thermal elasticity change.

The electro-mechanical brake (EMB) of Vienna Engineering (VE) uses a highly non-linear mechanism to create the high pressing force of the pad. The advantage is that the pad moves very fast when the pad pressing force is low and moves slower with increasing pressing force. The normal force in EMBs is often controlled by observing mechanical deformation to conclude to stress or force, commonly using strain gauges. It causes costs of the gauge itself and attaching them to e.g. the caliper and a sensitive amplifier. The full gauge equipment goes into the safety-related brake control system. The faintest damage (e.g. stone impacts, heat) gets the vehicle to the repair shop making expensive replacement necessary. To avoid the costs of the force measurement in the safety related system VE took the electrical motor measurements from the very beginning of the brake development for EMB control.