hub motor not running correctly

Hi,

We are building a rover with 2 drive wheels. Whe use 2 brushless hub motors (24V/350W) with hall sensors. The controler is a VBL2360, with a 24V battery.

With no load, i can drive the 2 wheels without problems.

With a small load, the motor are not rotating. I can stop the (10") wheel with my hand.

When I try to run the robot, it can't go at low speed, and the controller can't manage to drive the 2 wheels at the same speed.

I've noticed that the feedback in roborun+ is quite jerky on one motor (right one in forward direction, left one in reverse).

I've checked the sensor output with a scope, and it is ok, with or without load.

Any idea ?

I do have the problem in open and closed loop mode.

In the four folowwing tests:
- open loop, no load
- open loop, small load
- closed loop, no load
- closed loop, small load

I have a constant speed, and the same speed for right and left in only one case : closed loop with no load.

I've tried many settings for acc/decceleration, pid (most of the tests are done with P=0 or 0.2, I=2, D=0)

Hi,

the problem was the motor. I bought another pair of wheel with hub drive, and they work the same in the two directions.

I still have a torque problem when the motors have a 0 speed : the starting is really jerky. I tried many pid settings, the best ones are with I=20, P=5, D=0, but it's not good enough (sometimes, it is so jerky that it does'nt start to spin).

Did I miss something ?

Stephane