Max speed issue (direction switching) with Parallax Motor Mount/position contro

bulkhead

When the maximum travel speed is set faster than the motor can physically travel at, the motor will run at full speed for a few seconds, then suddenly (instantaneously, no ramping) switch directions and rotate for a few more seconds, the switch back again in an ongoing cycle. The time period between subsequent direction switches appears to increase after each direction switch.

Is this a known issue or is there something else wrong?

Edit: I'm using the Parallax 12V motors/position controller combo with the HB-25.

Post Edited (bulkhead) : 12/7/2008 11:31:50 AM GMT

Franklin

Could we see your code?

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
- Stephen

Mike Green

Sounds like a power supply problem, possibly resetting the controller. Neither the speed controller nor the HB-25 "know" how fast the motor can go. Probably the current drain of the motor peaks as it reaches maximum speed with friction increasing the mechanical load on the motor.

Beau Schwabe

bulkhead,

What is the current rating of your motor?

Besides motor abuse, throwing a motor into reverse like that can send current surges at least twice the motor rating if not more through the motor controller.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe

IC Layout Engineer
Parallax, Inc.

bulkhead

I'm sorry if I wasn't clear before but I am using the Parallax 12V motor kit. The HB-25's each have their own set of batteries that are isolated from the main microcontroller (Propeller protoboard). The position controllers are powered from the +5V on the protoboard. I just verified that they aren't resetting when the motor reverses direcitons; the position count from the encoder still continues (just in reverse direction) and the Propeller is still outputting debug info to the terminal.

I generated the problem by setting a value of 100 counts per half second as the max speed and then setting a distant position (10,000) for the motor to go to, where the actual maximum speed achievable by the motors is around 48 counts per half second (determined by querying the speed). Setting lower maximum speeds below 48 results in the motors functioning properly, as far as I could tell. Does this happen to anyone else?

Right now I'm setting a max speed below 48 so I don't run into this issue; everything else is working fine. Also, this problem occurs with both of the motor/position controller/hb-25 sets, left and right.

GWJax

PM Stampnuts about this and see if he can duplicate your program since I know he has the parts needed to run your code and setup and make sure you tell him I sent you to him as we are both are firends and we can work out your problem togeather or it just may be that the 48 counts per sec is all you can do with these motors.

Jax

ps please send me your code as well so I can look at it and make changes to it just incase. PM me and I'll send you my personal e-mail

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
If a robot has a screw then it must be romoved and hacked into..

bulkhead

Jax, I just attached a short test program that generates the error for me. It won't compile until you fill in the pin # for the FullDuplexSerial uart.

Here is the basic code that generates the problem:

CON     

   'position controller commands
  TRVL = %00100_000
  SMAX = %01000_000
 
...

     motorUart.start(9,9, %1100, 19200)
    
    'set max speed to 100 counts/half second    
    motorUart.tx(SMAX) '0 device ID, so send to all devices
    motorUart.tx(0)
    motorUart.tx(100)

    'set distant position to travel to (40*256 =10240)
    motorUart.tx(TRVL) '0 device ID, so send to all devices     
    motorUart.tx(40)
    motorUart.tx(0)

GWJax

I'll look over this program and see if anything pops out at me inwhich woud cause your problem. Since StampNuts lives in NZ he won't get your message until around 11 or 12pm tonight EST but I can catch up with him in the morning before he goes to bed.

Jax

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
If a robot has a screw then it must be romoved and hacked into..