[yusukeand]

Hi,

I was asked to implement a firmware for controlling an servo motor using an AC servo driver. The motor must be computer controlled and it is going to be used for simulating a car steering wheel with force feedback. Although I have already designed the firmware to communicate with the computer, I have no idea how to simulate the car steering wheel.

Any help, direction, document will be appreciated.

Yusuke
PS. Due to my level of dispair I am even considering vive away a few bucks via PayPal to the one who wishes to help. :-)

[Zenji]

Probably hook up some load sensing device to a gokarts steering and harvest all the information, go karts tend to be the most arcade like of vehicles.

[mike_Kilroy]

so you want a steering wheel on top for someone to turn and touch and stuff, and below something hooked to it that makes if 'feel' like a real steering wheel and give your computer feedback that lets you close the loop and make it happen?

We do that all the time for aircraft joysticks in simulators, even have our motors inside steering wheels being used to drive cars for gov testing agencies. all use a servo motor with position feedback, servo drive, motion controller. Your control simply watches the position feedback and adds the torque to resist the motor or make the motion as need be. What is the question? Just pick the properlyo sized servo motor, then get is matching servo drive, then apply your programming?

[yusukeand]

so you want a steering wheel on top for someone to turn and touch and stuff, and below something hooked to it that makes if 'feel' like a real steering wheel and give your computer feedback that lets you close the loop and make it happen?

We do that all the time for aircraft joysticks in simulators, even have our motors inside steering wheels being used to drive cars for gov testing agencies. all use a servo motor with position feedback, servo drive, motion controller. Your control simply watches the position feedback and adds the torque to resist the motor or make the motion as need be. What is the question? Just pick the properlyo sized servo motor, then get is matching servo drive, then apply your programming?

Zenji, thank you for your answer.

mike_Kilroy what I need is exactly that! thank you for replying.

I have already selected the properly sized AC servo motor and also the servo drive.

I intent to do use the Servo AC drive as follows, please correct if I am wrong, I will use a microcontroller :

1 - To read the Encoder Signal Outputs ( A, /A, B, /B, Z, and /Z)
This way I will be able to put the virtual steering wheel in the computer in the correspondent position (car simulator).

2 - To apply the Position Control Mode rotate the steering wheel
When the simulation starts, the steering wheel will rotate clockwise until the limit and then counter-clockwise.

The problem is: how do I make the steering wheel is harder to turn?
If I do not apply torque to the servo motor, it will stay easy to turn. If I apply torque the steering wheel to the opposite direction of the driver movement, it will become harder to turn. However, I believe this may not be the correct approach because:

- what if the driver stays holding the steering wheel and the motor be conntinuosly applying torque, would not the motor current increase a lot? or would the servo drive limit the current?

- what if the driver releases the steering wheel, since the microcontroller is applying torque, the steering wheel would go to the desired position. But I do not want it to go to any specific position, just want to make harder to move.

Thank you in advance.
yusuke

[mike_Kilroy]

The problem is: how do I make the steering wheel is harder to turn?
If I do not apply torque to the servo motor, it will stay easy to turn. If I apply torque the steering wheel to the opposite direction of the driver movement, it will become harder to turn. However, I believe this may not be the correct approach because:

- what if the driver stays holding the steering wheel and the motor be conntinuosly applying torque, would not the motor current increase a lot? or would the servo drive limit the current?

- what if the driver releases the steering wheel, since the microcontroller is applying torque, the steering wheel would go to the desired position. But I do not want it to go to any specific position, just want to make harder to move.

Thank you in advance.
yusuke

That is correct; you apply counter torque. You solve both your objections by algorithms YOU write in your micrprocessor position control program; since you know actual position, you will know instantly if person lets go or not.

I would recommend you place the servo drive in TORQUE mode and have your controller send command for torque to it directly - that way YOU have full control over position, velocity, and torque.

Just curious, are you using a motion controller like Galil or Delta Tau or just doing it all yourself? Since you have these questions, I would suggest you consider buying a controller from the equiv of one of the two I mentioned.

[XTCNC]

I should be pretty easy to do, theoretically you should be able to use the servo drive in torque and position mode.
You set the position as the centre of the steering wheel ( you can use the internal position in the servo drive which reads the position from the motor encoder), then set the torque limit parameter to the amount of force feedback you need.
When you turn the steering wheel the motor will always try to go to the centre (as with a car) giving you a force feedback, if you let go of the steering wheel, it will move to the centre and stay there. The servo drive will limit the current to the given torque, so that will be no problem.

[tinacnc]

servo drive and motors can used for cnc router machines.do u think servo drivers is the betters than stepper for the cnc engraving machine