Automotive BLDC control

Support for creating custom user applications on the VESC.
trucklodedad
Posts: 5
Joined: 14 Jun 2017, 14:19
Location: Seattle

Automotive BLDC control

Postby trucklodedad » 14 Jun 2017, 14:35

I have a 1977 Chevy C20 hot rod that I am almost ready to turn the key except for one small piece...crankcase vacuum pump. I have decided that to maximize efficiency it would be best to drive this vacuum pump with an electric motor. The only motors that have found with the right torque and RPM are BLDC motors. I have an aftermarket Holley ECU controlling the EFI, transmission and various additional electrical accessories I have added to the truck. The ECU has CANBUS (although I don't know the protocol yet) and programmable PWM outputs. The PWM is programmable from 1 to 1000Hz in 12VDC PWM+ or PWM-. The duty cycle is programmed into an X and Y axis table based on the selected inputs, in my case it will be crankcase pressure via a 1 bar MAP sensor plumbed to the crankcase. I want to know how to interface the VESC to ECU to control BLDC motor speed. Is this possible with some VESC programming?

Leon
Posts: 3
Joined: 24 Apr 2017, 11:15
Location: Gothenburg

Re: Automotive BLDC control

Postby Leon » 15 Jun 2017, 12:09

Use standard CAN based communication between the VESC and your ECU, where the ECU sends reference speed values to the VESC. Then there is the work with mapping electric motor speed to a certain amount of pressure desired by the ECU.

pf26
Posts: 278
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: Automotive BLDC control

Postby pf26 » 15 Jun 2017, 12:42

You probably better sent duty cycle references to the VESC instead speed references. To avoid strungling to adjust some speed PID control parameters..

trucklodedad
Posts: 5
Joined: 14 Jun 2017, 14:19
Location: Seattle

Re: Automotive BLDC control

Postby trucklodedad » 15 Jun 2017, 14:07

Just got off the phone with Holley...proprietary CANBUS protocol...they don't play well with others. Programming the MAP is easy enough, so I am back to 12vdc PWM+ or PWM-. I know the ECU is not outputting a typical PWM voltage, but maybe the PWM- is the way to go here. Any ideas would be greatly appreciated.

pf26
Posts: 278
Joined: 28 Mar 2016, 14:37
Location: FR Valence

Re: Automotive BLDC control

Postby pf26 » 16 Jun 2017, 07:26

With a 12V PWM at 1000Hz, you can use an RC filter (something like 1KOhm - 2.2uF) and then a voltage divider (4.7K-2.2K) to get a voltage ranging from to 0 to 3.3V approximately depending on the PWM duty cycle. Then you can use this voltage as the analog input of the VESC.

rew
Posts: 904
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Automotive BLDC control

Postby rew » 17 Jun 2017, 11:17

Doesn't the PWM input module support "regular" PWM? (as opposed to "RC servo" PWM)

trucklodedad
Posts: 5
Joined: 14 Jun 2017, 14:19
Location: Seattle

Re: Automotive BLDC control

Postby trucklodedad » 06 Jul 2017, 00:31

I believe it uses radio controlled frequency PPM or variable voltage inputs. I am going to get this going but still would like a little more direction on how to set up this application. If someone could point me in the right direction where to read up on programming / hardware required to make this work.
Thank you for all of your help so far.
Peter

rew
Posts: 904
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Automotive BLDC control

Postby rew » 06 Jul 2017, 06:16

Configure the PWM output for 1000Hz. Connect it to a 10k resistor and then to a 2.7k resistor and then to ground. Now put a 1uF capacitor in parallel to the 2.7k resistor. The junction between the 10k and the 2.7k resistor is the analog input for your VESC.

trucklodedad
Posts: 5
Joined: 14 Jun 2017, 14:19
Location: Seattle

Re: Automotive BLDC control

Postby trucklodedad » 11 Jul 2017, 14:37

Thanks for the reply rew. The rc filter part is to smooth the PWM signal into a variable voltage. I would also just like to confirm that this input connects to P3-3 ADC_EXT and no additional VESC programming is necessary for this to drive a BLDC motor, maybe some tuning.

rew
Posts: 904
Joined: 25 Mar 2016, 12:29
Location: Delft, Netherlands.

Re: Automotive BLDC control

Postby rew » 11 Jul 2017, 17:02

I don't have an original VESC myself. So where to connect it precisely is not my expertise.

Right. You'll have to configure the VESC to do "analog input" and maybe some tuning for your motor.


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