Wheel feedback electrics

Hi all, I know this seems to be an infrequently visited part of the forum but i'm hoping that someone here can offer some real information. I have searched this forum and all over the internet but i can not seem to find a good solution to my problem.

Basically, I have designed/made a wheel with an optical encoder as the sensor that is also hooked to a large DC motor (from an electric scooter) and i hope to use it for a simulated force feedback (not actual, more like 'dynamic force')

The Optical encoder and joystick interface is working fine. I am using an Arduino Nano to read the encoder and generate a PWM signal for the motor output. It also sends data to a 'Teensy' (Somewhat of another type of arduino) in joystick mode.

The joystick part of it is all working fine, as is a 31khz PWM signal ready for driving a H Bridge. I made a H bridge which works acceptable at lower PWM frequencies but then it is Audible/vibrates. However, if i bump up the frequency, the force is pretty much 0 until it gets to about 80-90% duty cycle.

The H Bridge i made is based on a HIP4081 H Bridge driver and 4 X STP80NF55 FETS (55v, 80A). Design comes from Nuts and volts - www.parallax.com/dl/docs/cols/nv/vol2/col/nv52.pdf and this is the last piece of the puzzle and I don't know if i am better off buying some sort of motor driver or whether some tweaks to the existing H Bridge is all that is needed.

Some on here have talked about 'AMC for $30 on ebay' but i don't know what they are and if i am better off trying to use one of them instead of the DIY H Bridge.

What are those of you with HAPP wheels using to drive the motor???

Hi,

I am using an AMC to drive my Happ wheel motor, controlled by a home made force feedback board (http://www.racedepartment.com/forum/thr ... ler.37051/).

The force feedback data returned by the games is a torque value, so when you drive a PM DC motor you have to control the current passing through the windings, via a current sensor.

Are you sure that your driver/transistors work with such frequency/current (oscilloscope traces ?) ?

And to avoid too high current ripple (and torque ripple) the PWM frequency of your H Bridge have to match the time constant of your motor.

Finding a suitable FFB motor is really not easy (cogging torque, stall torque/current, speed, cost, ...).

What power is your motor and what is the gear ratio ?

Hey, this is somewhat in my realm of expertise, so I'll take a crack at it. You say it's working fine at lower frequencies, but not so much at higher frequencies, correct? Is it a sudden drop off? Or does it get slowly worse as you increase the frequency? Do you have an oscilloscope you could look at the gates of the FETs with? What size of bootstrap capacitor are you using?
It's just a hunch, but the onboard gate drive power supply only supplies 39uA, so it might not be supplying enough to fully charge the bootstrap capacitor to turn on the FETs, or the bootstrap capacitor is not having enough time to charge during the OFF cycle. Try turning the measuring the voltage of the BHB and AHB pins on the HIP4081 during this fault condition. They should be near 12.8V.

EDIT: also, do you have another link for that reference design? That one's not working for me. If the reference design calls for resistors on the gate of the FET, how large are they?

Must be the day for it = replying to a post from 2012 . Good luck .

Doh! How did I not notice that? Guess I thought I must have been browsing the recently posted section