Creep Function Architecture

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cpwl

Well-known member
Joined
May 9, 2014
Messages
71
Location
Gatineau, QC, Canada
Does anyone know the architecture of the “creep” function in our FFEs. Clearly the motor and drive train is not constantly working against the brakes when stopped as is the case in an ICE’s automatic transmission. But what is the input “trigger” to start the motor when the brakes are released (either fully or partially). Is it a sensor in the brake line that detects a release of brake pressure, is at position or limit switch on the brake pedal mechanism itself, or something totally different. And does anyone know anything about the basic software as to power limits during creep etc.?

Thanks and Cheers

Carl
 
cpwl said:
Does anyone know the architecture of the “creep” function in our FFEs. Clearly the motor and drive train is not constantly working against the brakes when stopped as is the case in an ICE’s automatic transmission. But what is the input “trigger” to start the motor when the brakes are released (either fully or partially). Is it a sensor in the brake line that detects a release of brake pressure, is at position or limit switch on the brake pedal mechanism itself, or something totally different. And does anyone know anything about the basic software as to power limits during creep etc.?

Thanks and Cheers

Carl
Using FORScan I've been able to observe that as you lift off the brake pedal the HVB starts supplying power to the motor to start the creep function. Creep seems to be about 2 kW of power to the wheels. There are points where your foot is on the brake but the HVB is supplying power to the motor to fight against the brakes, this is how you can control the creep speed with your foot on the brake.
 
You would have to start by understanding the operation of the braking system. The brakes are run entirely by the electronic control system and there is no direct connection between the pedal and the brake system unless a fault occurs.

http://www.natef.org/NATEF/media/NA...onf Presentations/Lesson-2-Braking-System.pdf

I don't know how they've implemented the creep function, but there wouldn't necessarily have to be any use of or interaction with the friction brakes.
 
Wow; can you post links to the other Lessons about the Focus Electric? That one is pretty interesting and seeing that it is lesson 2 I'd be interested in seeing lesson 1 and more if there are any?

Well here is lesson 3:
http://www.natef.org/NATEF/media/NATEFMedia/ASEIEA%202014%20Instructor%20Conf%20Presentations/Lesson-3-Cooling-System.pdf

and a vehicle overview:
http://www.natef.org/NATEF/media/NATEFMedia/ASEIEA%202014%20Instructor%20Conf%20Presentations/Vehicle-Overview.pdf
 
The brake section is very interesting. I had an argument with a Tesla driver. He claimed that blended braking was inefficient because applying the brake pedal would inevitably drag the friction brakes. I had read that the Honda FIT EV had a valve which prevented any friction braking until regenerative braking was insufficient and I had wondered whether Ford was clever enough to provide this feature by one means or another.

Turns out they were!
 
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