New to 2CAN and Jaguar

[mikets]

Originally Posted by jhersh

As long as you are getting a timeout from a send message call, there is something wrong with either your wiring or your configuration.

Wiring should be fine. I have tested it with the bdc-comm-100.exe tool and was able to see and run all motors. So it means the CAN bus is good. I am also able to see the 2CAN and all the Jags on the network (i.e. can access the 2CAN dashboard on 10.4.92.10 and see the status of all the jags). So it means the ethernet connection to the 2CAN is good. What other wiring could be wrong?

Originally Posted by jhersh

Once you get past that, then you'll need to make sure you are calling all the right methods to enable the closed-loop control. Your first code snippet was much closer than this most recent post.

Yeah, I decided to redo the program with standard template and thinking I don't care about the encoders yet so I skipped the encoder related initialization. So you are saying they are still required?

[jhersh]

Originally Posted by mikets

Wiring should be fine. I have tested it with the bdc-comm-100.exe tool and was able to see and run all motors. So it means the CAN bus is good. I am also able to see the 2CAN and all the Jags on the network (i.e. can access the 2CAN dashboard on 10.4.92.10 and see the status of all the jags). So it means the ethernet connection to the 2CAN is good. What other wiring could be wrong?

Probably nothing. Are you checking for errors or messages on the console being printed by the 2CAN plugin? Have you tried a BlackJag bridge?

Originally Posted by mikets

Yeah, I decided to redo the program with standard template and thinking I don't care about the encoders yet so I skipped the encoder related initialization. So you are saying they are still required?

They are required for closed loop mode... without some process variable, the controller does nothing. You may want to try simple PercentVbus mode first. Start simple and all. Verify you can talk to the Jags at all. Make sure your device numbers in the constructors match what you configured.

[mikets]

I changed the program as you suggested (new code attached). Notice that I added the jag.Set(30.0) in there outside of the loop. When running it, I heard the motor noise like it had moved but then stopped. When I looked, nothing happened. Then I noticed my voltage is getting low and the Jags are no longer powered. I think my battery is now exhausted. Unfortunately, the mechanical mentor has the charger. So I guess I am done for tonight. But I am excited, it may mean the motor really moved but then the battery died because of the current drawn. If that's the case, it means the jag.Set() outside of the loop worked. If so, the next step is to find out why the ArcadeDrive inside the loop did not work. Since you suggested "speedJag.Set(stick.GetAxis(axis) * 150.0);", does it mean the full range of the Jag is -150.0 to 150.0? How about the ArcadeDrive call? Would the RobotDrive object do the scaling to 150, or do I need to call SetMaxOutput myself? I can't find anywhere in CANJaguar that it scales the outputValue. If that's the case, that explains why the motors didn't move because the outputValue will be below or equal to 1.0 in a full scale of 150.0. I thought everything in WPILib scaled to 1.0. Why is it that we need to multiply 150.0 in jagSpeed.Set()? If the speed mode is really in the range of -150.0 to 150.0, is there documentation somewhere telling me what range is the motor in which mode?

[mikets]

Wait, I found the scaling code in CANJaguar. It is in packFXP16_16. It means the full range is actually +/- 65536. So like I suspected, the outputValues in jag.Set() should always be in the range of +/- 1.0 and the CANJaguar module will scale it to +/- 65536 and send it to the jags. Then why do we need to multiply 150.0? I am confused.

[jhersh]

Originally Posted by mikets

Wait, I found the scaling code in CANJaguar. It is in packFXP16_16. It means the full range is actually +/- 65536. So like I suspected, the outputValues in jag.Set() should always be in the range of +/- 1.0 and the CANJaguar module will scale it to +/- 65536 and send it to the jags. Then why do we need to multiply 150.0? I am confused.

The actual range depends on the mode. Look at the documentation for CANJaguar::Set.

/**
 * Set the output set-point value.  
 * 
 * The scale and the units depend on the mode the Jaguar is in.
 * In PercentVbus Mode, the outputValue is from -1.0 to 1.0 (same as PWM Jaguar).
 * In Voltage Mode, the outputValue is in Volts.
 * In Current Mode, the outputValue is in Amps.
 * In Speed Mode, the outputValue is in Rotations/Minute.
 * In Position Mode, the outputValue is in Rotations.
 * 
 * @param outputValue The set-point to sent to the motor controller.
 * @param syncGroup The update group to add this Set() to, pending UpdateSyncGroup().  If 0, update immediately.
 */

Everything you see inside the CANJaguar class is to convert from the WPILib API formats (such as -1.0 to 1.0) into the binary format to send to the Jag. Since in speed mode, the units are RPM, I don't want to control my motor +/- 1 RPM... that's too slow. I set the RPM range in my example to +/- 150 RPM cause it made sense for the mechanism I was sensing with that encoder.

In the case of RobotDrive, it computes a motor output +/- 1.0 based on joystick inputs. If you are not using motors in Percent Vbus mode, then that's probably not a good range. The RobotDrive class allows you to specify a scale value by calling SetMaxOutput(); with a floating point number to multiply by the +/-1.0 values that it computes before they are passed into the Set(); call on each motor.

Hope that's clearer.

-Joe

[mikets]

Ah, I missed the comments in the code. It must be too late in the night. Thanks. That's much clearer.

[mikets]

Actually, few more questions: is the kPercentVbus mode essentially kVoltage but just scale to the range of -1.0 and 1.0? Only kSpeed and kPosition modes use encoder/potentiometer? Are kVoltage and kCurrent modes also considered close-loop modes? To me, close-loop means feedback. Monitoring output voltage and current so it can maintain constant values seem close-loop to me too even though it is not using any "external sensors" such as encoder and potentiometer.

Thanks.

[jhersh]

Originally Posted by mikets

Actually, few more questions: is the kPercentVbus mode essentially kVoltage but just scale to the range of -1.0 and 1.0? Only kSpeed and kPosition modes use encoder/potentiometer? Are kVoltage and kCurrent modes also considered close-loop modes? To me, close-loop means feedback. Monitoring output voltage and current so it can maintain constant values seem close-loop to me too even though it is not using any "external sensors" such as encoder and potentiometer.

Thanks.

Voltage mode is different. Lets take two cases:

If your battery voltage is 12V and you specify 0.5 in PercentVbus mode, you get 6V and if you specify 6V in Voltage mode, you get 6V.

If your battery voltage is 9V and you specify 0.5 in PercentVbus mode, you get 4.5V and if you specify 6V in Voltage mode, you get 6V.

Position, Speed, and Current (the sensor is inside the Jag, but external to the controller) are closed loop modes that use a PID algorithm with feedback. The Voltage mode is not closed loop because the setting is simply scaled based on the bus voltage, not corrected based on the resulting output. This is because unlike the other modes, the voltage can be controlled directly.

-Joe

[mikets]

I got it to work now. Here is what I learned:
- My encoders are not working, it could be the cable. We will figure that out later.
- Apparently, if I do kSpeed mode, the motors jerk back and forth violently. Sort of vibrating loudly. That gave me the hint that the encoders are not working. I added a call to GetPosition and saw only zeros.
- So I changed the code to use kVoltage mode and scale the joystick values by multiplying with 12.0. This doesn't work either.
- Then I thought since the encoders are not working, I would disable all the encoder related initialization. To my surprise, that works. I would have thought the encoder is ignored when doing kVoltage mode, but apparently not.
- With the encoder initialization disabled, I changed the code to use kPercentVbus mode and removed the 12.0 multiplier. That also worked.

So the robot is totally tele-operating. Next step is to figure out what's wrong with the encoders.

[jhersh]

Originally Posted by mikets

So the robot is totally tele-operating. Next step is to figure out what's wrong with the encoders.

Congrats! About the encoders affecting the Voltage mode, that should not be the case. Usually when something like that happens it means you got an error other than a timeout and the object has given up talking to the Jaguar until you either fix your code and rerun, or you call ClearError() on the object. Check for errors.

-Joe

[mikets]

Now that the Jags run successfully in kPercentVbus mode as well as kVoltage mode as long as all the Encoder related initializations are commented out, I am investigating what exactly caused this. I have isolated the culprit. It looks like all the encoder initializations are fine except for the SetPID calls. So basically, the following code doesn't work until I comment out the CULPRIT_CODE lines. Note that the Jags are initialized to kPercentVbus mode. Kp is 15.0, both Ki and Kd are zeros. What could have caused this?

class MyRobot: public SimpleRobot
{
private:
    CANJaguar m_jagLeft;
    CANJaguar m_jagRight;
    Joystick m_leftStick;
    Joystick m_rightStick;
 
public:
    MyRobot():
        m_jagLeft(CANID_LEFT_JAG, CANJaguar::kPercentVbus),
        m_jagRight(CANID_RIGHT_JAG, CANJaguar::kPercentVbus),
        m_leftStick(JOYSTICK_LEFT),
        m_rightStick(JOYSTICK_RIGHT)
    {
        m_jagLeft.SetSpeedReference(CANJaguar::kSpeedRef_QuadEncoder);
        m_jagRight.SetSpeedReference(CANJaguar::kSpeedRef_QuadEncoder);
 
        m_jagLeft.SetPositionReference(CANJaguar::kPosRef_QuadEncoder);
        m_jagRight.SetPositionReference(CANJaguar::kPosRef_QuadEncoder);
 
#ifdef _CULPRT_CODE
        m_jagLeft.SetPID(DRIVE_KP, DRIVE_KI, DRIVE_KD);
        m_jagRight.SetPID(DRIVE_KP, DRIVE_KI, DRIVE_KD);
#endif

        m_jagLeft.ConfigEncoderCodesPerRev(DRIVE_ENCODER_CODES_PER_REV);
        m_jagRight.ConfigEncoderCodesPerRev(DRIVE_ENCODER_CODES_PER_REV);

        m_jagLeft.EnableControl();
        m_jagRight.EnableControl();
    }
 
    ....
    ....
    ....
    void OperatorControl(void)
    {
        while (IsOperatorControl())
        {
            m_jagLeft.Set(-m_leftStick.GetY());
            m_jagRight.Set(-m_rightStick.GetY());
            Wait(0.005);
        }
    }
};

[jwakeman]

I don't know if this is your problem but kp=15 doesn't seem right. I was doing current control mode with the jags last night and i was using Kp=0.01 and Ki = 0.05. Regardless if you are in percent vbus mode I would think the PID gains should have no effect.