Right-hand channel on the front wheels Note 2. Tesla vehicles use the ESP hev II unit with the left-hand channel on the rear wheels and the Together, these ESP hev II modifications support brake blending operations in a hybrid electric vehicle. This also requires a special kind of pressure relief valve as shown in yellow in Figure 25. This prevents the driver from feeling the electrically activated brake pressure in this channel. Therefore, Bosch has modified its existing ESP 9.0 modulator for this purpose by returning the brake fluid from one channel back to the fluid reservoir instead of the master cylinder as shown on the left channel in Figure 25. In hybrid electric vehicles, it is often desireable to prevent the driver from feeling the electrically activated brake pressure in order to hide changes in the manually operated brake pressure caused by brake blending operations associated with regen. When electrical activation is used on either channel, the driver can feel the brake pressure provided by the electrically activated pressure pump as it is fed back into the master cylinder via a pressure relief valve, as shown by the right hand channel in Figure 25. This electrical activation can be done on either channel separately while the other channel is operated manually or on both channels at the same time. Besides mechanical activation of the brakes by the brake pedal, the system also allows electrical activation independently of the brake pedal by closing the isolation valves from the master cylinder and activating the pressure pumps to provide the desired brake pressure to the wheels. The valves are shown in their normal operating positions when power is off, which allows the transfer of pressurized brake fluid from the master cylinder to the wheels to allow normal manual operation of the brakes. Response time for commands is one millisecond to enable fast braking operations in emergency situations.įigure 25 shows how the iBooster and the ESP hev II brake modulator work together to achieve brake operation. Module receives commands from the iBooster via a high speed serial CAN bus. Figure 24 shows that the unit consists of over twelve electrically operated solenoid valves of various types, two hydraulic pressure pumps, an electric motor to operate the pressure pumps, a PID controller with feedback control and high power drive transistors to operate the electric motor, accumulators, pressure sensors, and an overall electronic control module for issuing commands to the pumps and solenoid valves. It is a special version of Bosch’s newest ESP 9.0 ABS modulator that is specifically adapted for use in hybrid electric vehicles. The brake modulator unit used in Tesla’s brake system is Bosch’s ESP hev II module as shown in Figure 23. Tesla Regen, Brakes and Sudden Acceleration Front brakes provide feel rear brakes can blend regen up to. I found this fairly interesting writeup of the braking system Tesla.
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