In velocity mode index_search failed

Meekdai commented 4 years ago

Hi @askuric , I set up a simple test environment, I use arduino 2560 and my motor drive DRV8840. When I set the index pin:

Encoder encoder = Encoder(arduinoInt1, arduinoInt2, 128, A0);

Connect the A0 pin to the index of the encoder, The motor rotates, but it can never be completed.

DEBUG: Serial debugger enabled!  
DEBUG: Initilaise the motor pins.
DEBUG: Set high frequency PWM.   
DEBUG: Enabling motor.
DEBUG: Align the encoder and motor electrical 0 angle.
DEBUG: Search for the encoder index.

I tried not to use the index pin, set it to 0, I successfully entered

DEBUG: Serial debugger enabled!  
DEBUG: Initilaise the motor pins.
DEBUG: Set high frequency PWM.   
DEBUG: Enabling motor.
DEBUG: Align the encoder and motor electrical 0 angle.
DEBUG: Index not available!
Motor ready.
Input the new target velocity:

Through motor_monitor (); I can monitor my motor status very well. But when I input the velocity value between 0-450, the motor will jitter irregularly. After setting the velocity value greater than 500, the motor works well, but the speed will be maintained at around 460 even if I increase the velocity value.

I don't know if this is related to the parameters of PID.

the motor i used 483068

Meekdai commented 4 years ago

This is part of the data with velocity set to 10：

-0.15   10.00   21.23   20.48
-0.76   10.00   29.79   20.53
-0.16   10.00   13.34   20.57
-0.76   10.00   16.49   20.59
-0.17   10.00   8.49    20.62
0.11    10.00   8.49    20.62
0.38    10.00   8.49    20.62
0.66    10.00   8.49    20.62
0.93    10.00   8.49    20.62
1.50    10.00   1.33    20.63
0.92    10.00   8.98    20.65
0.33    10.00   22.20   20.71
-0.29   10.00   34.54   20.80
-0.91   10.00   29.27   20.87
-1.52   10.00   26.54   20.95
-0.92   10.00   16.44   20.98
-1.48   10.00   16.44   20.98
-0.88   10.00   -5.72   20.96
-0.28   10.00   -25.07  20.90
0.34    10.00   -35.06  20.81
0.97    10.00   -31.31  20.73
1.58    10.00   -27.10  20.65
2.20    10.00   -17.73  20.60

This is part of the data with velocity set to 500：

12.00   500.00  173.31  1041.56
12.00   500.00  179.83  1042.22
12.00   500.00  185.83  1042.91
12.00   500.00  190.66  1043.63
12.00   500.00  194.30  1044.38
12.00   500.00  201.62  1045.17
12.00   500.00  202.79  1045.99
12.00   500.00  216.05  1046.84
12.00   500.00  213.23  1047.72
12.00   500.00  226.79  1048.65
12.00   500.00  228.86  1049.62
12.00   500.00  233.40  1050.62
12.00   500.00  239.97  1051.65
12.00   500.00  250.69  1052.74
12.00   500.00  253.21  1053.87
12.00   500.00  253.74  1055.02
12.00   500.00  266.02  1056.23
12.00   500.00  265.82  1057.49
12.00   500.00  276.62  1058.78
12.00   500.00  277.45  1060.14
12.00   500.00  286.70  1061.54
12.00   500.00  293.30  1063.00
12.00   500.00  299.82  1064.51
12.00   500.00  307.53  1066.13
12.00   500.00  310.52  1067.74
12.00   500.00  316.88  1069.45
12.00   500.00  321.20  1071.22
12.00   500.00  328.87  1073.09
12.00   500.00  334.89  1075.00
12.00   500.00  340.64  1077.00
12.00   500.00  345.66  1079.10
12.00   500.00  354.47  1081.31
12.00   500.00  357.96  1083.62
12.00   500.00  363.11  1086.06
12.00   500.00  370.44  1088.59
12.00   500.00  378.02  1091.27
12.00   500.00  383.72  1094.05
12.00   500.00  389.09  1096.99
12.00   500.00  395.28  1100.12
12.00   500.00  403.06  1103.44
12.00   500.00  414.18  1106.99
12.00   500.00  421.34  1110.85
12.00   500.00  426.33  1114.96
12.00   500.00  435.71  1119.39
12.00   500.00  440.19  1124.15
12.00   500.00  450.09  1129.40
12.00   500.00  463.42  1135.28
12.00   500.00  467.22  1141.93
12.00   500.00  486.70  1149.71
12.00   500.00  498.21  1159.30
5.14    500.00  516.07  1172.21
-9.98   500.00  552.14  1199.88
-12.00  500.00  522.67  1225.12
-11.01  500.00  187.28  1225.83
-10.10  500.00  154.32  1226.39
-9.24   500.00  133.22  1226.84
-8.43   500.00  115.93  1227.20
-7.64   500.00  105.50  1227.52
-6.90   500.00  81.81   1227.75
-6.18   500.00  69.20   1227.95
-5.49   500.00  56.99   1228.11
-4.81   500.00  42.76   1228.22
-4.14   500.00  31.09   1228.30
-3.49   500.00  19.95   1228.35
-2.85   500.00  13.54   1228.39
-2.23   500.00  13.54   1228.39

askuric commented 4 years ago

Hey @Meekdai, thanks for the message. Both of the problems are the problems of the PI contorllers I think. Try to tune them a bit better, in the code they are set for a BLDC motor I have with me.

Basically try to set:

// index search velocity - default 1rad/s
  motor.index_search_velocity = 1;
  // index search PI contoller parameters
  // default K=0.5 Ti = 0.01
  motor.PI_velocity_index_search.K = 2;
  motor.PI_velocity_index_search.Ti = 10;
  // jerk control using voltage voltage ramp
  // default value is 100
  motor.PI_velocity_index_search.voltage_ramp = 1000;

and something similar to :

  // contoller configuration based on the controll type 
  // velocity PI controller parameters
  // default K=1.0 Ti = 0.003
  motor.PI_velocity.K = 2;
  motor.PI_velocity.Ti = 10;
  motor.PI_velocity.voltage_limit = 10;
  // jerk control using voltage voltage ramp
  // default value is 300 volts per sec  ~ 0.3V per millisecond
  motor.PI_velocity.voltage_ramp = 3000;

Also make sure if you dont need the pull-ups for your encoder.

You can use the Arduino ones if you need them at by setting:

  encoder.pullup = Pullup::INTERN;

By the look on the log, it seems that your motor cannot reach 500rad/s with 12 volts? To put 500 rad/s in context you can calculate it to rpm:

500[rad/s] / (2*PI) * 60 = 4774rpm (rotations per minute)

I am not sure what your motor limit is but this might be close to it.

Meekdai commented 4 years ago

According to your suggestion, I tried some parameters and got better improvement.

  encoder.quadrature = Quadrature::ENABLE;
  encoder.pullup = Pullup::INTERN;
  encoder.init(doA, doB);
  motor.voltage_power_supply = 12;
  motor.index_search_velocity = 100;
  motor.PI_velocity_index_search.K = 0.5;
  motor.PI_velocity_index_search.Ti = 0.01;
  motor.PI_velocity_index_search.voltage_ramp = 20;
  motor.controller = ControlType::velocity;
  motor.PI_velocity.K = 0.5;
  motor.PI_velocity.Ti = 0.01;
  motor.PI_velocity.voltage_limit = 10;
  motor.PI_velocity.voltage_ramp = 20;

and the log:

0.61    200.00  192.80  13922.67
0.54    200.00  195.69  13923.45
0.48    200.00  201.40  13924.24
0.54    200.00  199.30  13925.05
0.47    200.00  203.42  13925.85
0.41    200.00  205.18  13926.67
0.34    200.00  205.84  13927.50
0.27    200.00  206.98  13928.33
0.34    200.00  204.10  13929.15
0.41    200.00  202.14  13929.97
0.34    200.00  206.28  13930.79
0.27    200.00  205.41  13931.60
0.34    200.00  201.93  13932.42
0.41    200.00  201.02  13933.23
0.34    200.00  203.42  13934.04
0.41    200.00  197.83  13934.85
0.34    200.00  203.86  13935.65
0.27    200.00  205.62  13936.49
0.34    200.00  199.94  13937.27
0.27    200.00  202.10  13938.07
0.20    200.00  202.32  13938.88
0.14    200.00  204.53  13939.66
0.20    200.00  195.69  13940.45
0.14    200.00  200.45  13941.21
0.20    200.00  191.95  13941.97
0.14    200.00  194.68  13942.73
0.20    200.00  189.17  13943.47
0.14    200.00  192.61  13944.19
0.20    200.00  191.53  13944.90
0.27    200.00  189.81  13945.62
0.33    200.00  186.78  13946.32
0.40    200.00  186.36  13947.01
0.46    200.00  181.49  13947.69
0.40    200.00  187.83  13948.40
0.46    200.00  190.66  13949.13
0.53    200.00  179.25  13949.81
0.50    200.00  185.11  13950.54
0.43    200.00  191.31  13951.25

But, the index pin still has no effect. I use an oscilloscope to measure the index pin signal and it looks normal when the motor is rotating.

Below are the parameters of my motor:

parameter	value
Nominal voltage	18 V
No load speed	10400 rpm
No load current	50.6 mA
Nominal speed	9190 rpm
Nominal torque (max. continuous torque)	29.1 mNm
Nominal current (max. continuous current)	1.85 A
Stall torque	297 mNm
Stall current	18.4 A
Max. efficiency	86 %

askuric commented 4 years ago

Hey @Meekdai , perfect! Ok so your motor is rated to 10400rpm on 18V given that the range is linear at 12V you should be able to have:

12V/18V * 10400rpm = 6950rmp ~ 750rad/s

So 500rad/s should not be the limit yet.

but keep in mind also that arduino has to count (128*4) impulses per revolution or for 500rad/s around 40,000 impulses per second. And that can be too much sometimes. So if you are going to spin the motor so fast for longer periods of time don't use quadrature mode.
```
encoder.quadrature = Quadrature::DISABLE;
```
If you are interested in positioning than you don't really need such high velocities anyway.

Regarding the index pin, I don't really know why it doesn't work. Your motor never finds the index? The motor spins and then you get the message:

DEBUG: Error: Index not found!

or you don't get even that?

askuric commented 4 years ago

You can do one simple test to see what's going on:

ISR (PCINT1_vect) { 
   encoder.handleIndex(); 
   Serial.print("Index interrupt triggered");
}

Then you can disconnect the motor and spin it by hand to see if this code is ever going to be executed.

Meekdai commented 4 years ago

Thanks @askuric , Your library is really great, let me successfully control the DC motor. I also learned a lot from it. I don’t have a high requirement for speed, so I hope to try position control.

Meekdai commented 4 years ago

Hi @askuric , Use A0 pin, When I Rotating the motor I can not get the message "Index interrupt triggered", So I use int.2 to encoder index pin.

Encoder encoder = Encoder(arduinoInt1, arduinoInt2, 128, 21);

void index(){
  encoder.handleIndex(); 
  Serial.print("Index interrupt triggered");
}
void setup() {
  Serial.begin(115200);
  attachInterrupt(2, index, FALLING);
}

When I Rotating the motor, I can get the message "Index interrupt triggered", but the log block at:

DEBUG: Initilaise the motor pins.
DEBUG: Set high frequency PWM.
DEBUG: Enabling motor.
DEBUG: Align the encoder and motor electrical 0 angle.
DEBUG: Search for the encoder index.

I don't get DEBUG: Error: Index not found! never.

askuric commented 4 years ago

Hey @Meekdai, the reason may be because I have considered index of the encoder to be rising edge signal. I am not sure why this code doesn't work properly for you.

I have chnaged the code a bit and pushed it to the master branch.

Basically now you will create the handler funciton

void doIndex(){encoder.handleIndex();}

And if you have enough interrupts you can put it into the encoder.init():

  encoder.init(doA, doB, doIndex);

or if you have only two for A and B, you do as before with this approach:

ISR(PCINTx_vect){doIndex;}

I hope it helps

Meekdai commented 4 years ago

Hi, @askuric good news.

DEBUG: Serial debugger enabled!
DEBUG: Initilaise the motor pins.
DEBUG: Set high frequency PWM.
DEBUG: Enabling motor.
DEBUG: Align the encoder and motor electrical 0 angle.
DEBUG: Search for the encoder index.
DEBUG: Success: Index found!
Motor ready.
Input the new target velocity:
0.00    0.00    0.00    0.38
0.00    0.00    0.00    0.38

Now it can find the index correctly！thanks a lot.

askuric commented 4 years ago

Hey @Meekdai, perfect! I am still not sure why the previous approach did not work, I will have to look into it a bit deeper.

Also I will create a library from this repo in next few days with a bit more examples. For now you I will upload another minimal example of the position control so you can test it.

Antun

Meekdai commented 4 years ago

Very thankful @askuric I tried angle before use my code, and I found that the serial input is invalid. I will test your example code for the first time tomorrow.

askuric / Arduino-Closed-Loop-Motor-Control

In velocity mode index_search failed #2