HPI Q32 review

[qatmix]

Check out this little buggy. I've really enjoyed it, and can see why they are pretty hard to get at the moment.

http://www.thercracer.com/2015/07/hpi-baja-q32-review.html

[backtomyroots]

Nice review -- that looks like the perfect "mouse" for my cat to chase about .

[speedy_w_beans]

The steering motor looks similar to the main drive motor; is there a centering spring the steering motor pushes against? That might explain some of the buzzing you're hearing when using the radio trims.

The traditional servo actually senses shaft angle and closes the loop on it, where a simple motor pushing on a spring is an open-loop approach. Using a trim on the radio is basically commanding a little bit of current to always be applied to the motor, and it's probably pulsed hence the buzzing. Using the trim on the chassis probably rotates the centering spring a little, and that doesn't change how much current is flowing through the motor when driving straight ahead.

I used to work for a controls company modeling servo control loops in Matlab, and we always closed the control loops on current, velocity, and position. Some of our competitors just offered a simple motor and return spring approach. We had the better performance and lower power consumption, but they had lower costs. Application specs drove which way the customers went.

For a small buggy like this the motor and spring approach probably works just fine.