I bet that there is not any velocity feedback from the motors, and the controller is just feeding each motor a voltage that is dependent on the position of the joystick. If the motors are permanent magnet they will run at a speed proportional to the voltage they get, but if the load on each motor is a different the speed of each motor will be a little different from its commanded speed. If the chair is running on a side slope the motor on the lower side will likely need to work harder and so will run slower. What you need is to close the velocity loop between the motors or the wheels themselves and the controller. How easy that is to do will depend on what signals are available, it may be possible to put something between the joystick and the controller. This would not compensate for the wheels slipping which the gyro could but I think it would be a lot less expensive. I do not know how good the model aircraft gyros are but it would need to be very sensitive and stable to correct for a slow drift.
Andre' B. [EMAIL PROTECTED] If something cannot be defined, it does not exist. Isaac Newton -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Mike Pengelly Sent: Tuesday, October 01, 2002 3:15 PM To: [EMAIL PROTECTED] Subject: Re: directional stability for tank drive > I was wondering if anyone had built a small tank drive like ev. From my use with chairs, I dont know if its the small motors or retarded programming, but they go with the slope. So, driving on the edge of the road, it pulls to the gutter. On a chair, you just move the joystick to about 10 oclock position to go in a line, but with less speed then before. > > My idea was to use a gyro to sense left and right movement and maybe rig this to the controls so it can compensate for this or for quick jerks in direction like if you hit a pot hole with one side or rut. > > Just an idea > > jeff > > richmond, va > > http://www.wheelchairmodifications.org Jeff, Interesting idea! If you want to look at gyros for this application you might try Piezo Gyros made for model aircraft. They are used for stabilizing model helicopters so they don't rotate. It appears they cost about $100. The fun part would be integrating the gyro signal to your controller. Mike Pengelly Phoenix, AZ '90 Mustang EV [EMAIL PROTECTED]
