I'm confused about COUNTS_PER_REV #67

Pattapol2005 · 2025-04-05T15:26:43Z

Pattapol2005
Apr 5, 2025

Hello, I encountered an issue with COUNTS_PER_REV. According to the manufacturer’s specifications, the encoder output is 245 pulses per rotation, with a single-channel output. I set COUNTS_PER_REV to 245, but when I tested movement using teleop and Navigation2, the robot moved very slowly, and the motor sound seemed abnormal.

So, I tested the encoder using the calibration utility and got a value of approximately 1300. I then set COUNTS_PER_REV to 1300, and when I tested it with teleop, the robot moved normally. However, when testing with Navigation2 and commanding the robot to move to a goal, the issue still persisted as shown in the video clip. What should I adjust or fix? Thank you.

Motor and Encoder specifications.

COUNTS_PER_REV 245

2025-04-05.20-26-39.online-video-cutter.com.1.mp4

COUNTS_PER_REV 1300 ( calibration )

2025-04-05.21-11-18.online-video-cutter.com.mp4

hippo5329 · 2025-04-06T01:11:00Z

hippo5329
Apr 6, 2025
Maintainer

You should run test_motors and verify the wheel rpm with a laser tachometer. Check the wiki.

1 reply

hippo5329 Apr 6, 2025
Maintainer

https://github.com/hippo5329/linorobot2_hardware/wiki#test-the-motors-and-encoders

hippo5329 · 2025-04-06T02:02:55Z

hippo5329
Apr 6, 2025
Maintainer

The movement of the robot is fine in your video. You can run test_acc to find the max acceleration. Then adjust the velocity smoother parameters.

2 replies

Pattapol2005 Apr 10, 2025
Author

I have already resolved the previous issue. The digital tachometer measured 160 rpm, while the test_motors utility reported 119 rpm. So, I adjusted the COUNTS_PER_REV value. Now both the digital tachometer and the test_motors utility report matching values.

However, when I use the Navigation2 tool, the robot rotates in the way shown in the attached image. Could you please suggest how to fix this? 🙏
I'm using a mecanum-wheel robot.

test_acc result

test_acc

02:16:29.972 -> MAX PWM 1023.0 -1023.0
02:16:29.972 -> MAX VEL   0.94   0.02 m/s    0.12 rad/s
02:16:29.972 -> MIN VEL  -0.94  -0.04 m/s   -0.10 rad/s
02:16:29.972 -> MAX ACC  20.45   1.15 m/s2    6.13 rad/s2
02:16:29.972 -> MIN ACC -19.76  -0.92 m/s2   -7.15 rad/s2
02:16:29.972 -> IMU ACC   6.02  -3.68 m/s2
02:16:29.972 -> time to 0.9x max vel   0.36 sec
02:16:29.972 -> distance to stop   0.04 m
02:16:29.972 -> BAT  0.00V MIN  0.00V
02:16:34.320 -> MAX PWM 1023.0 -1023.0
02:16:34.320 -> MAX VEL   0.02   0.02 m/s    4.04 rad/s
02:16:34.320 -> MIN VEL  -0.02  -0.02 m/s   -4.04 rad/s
02:16:34.320 -> MAX ACC   0.92   1.15 m/s2   88.83 rad/s2
02:16:34.320 -> MIN ACC  -1.15  -1.15 m/s2  -88.83 rad/s2
02:16:34.320 -> IMU ACC   4.02  -3.68 m/s2
02:16:34.320 -> time to 0.9x max vel   0.18 sec
02:16:34.320 -> distance to stop   0.15 rad
02:16:34.320 -> BAT  0.00V MIN  0.00V
02:16:38.664 -> MAX PWM 1023.0 -1023.0
02:16:38.664 -> MAX VEL   0.95   0.04 m/s    0.14 rad/s
02:16:38.664 -> MIN VEL  -0.95  -0.03 m/s   -0.08 rad/s
02:16:38.664 -> MAX ACC  20.45   1.61 m/s2    5.11 rad/s2
02:16:38.664 -> MIN ACC -20.22  -1.61 m/s2   -4.08 rad/s2
02:16:38.664 -> IMU ACC   4.98  -5.17 m/s2
02:16:38.664 -> time to 0.9x max vel   0.38 sec
02:16:38.664 -> distance to stop   0.04 m
02:16:38.664 -> BAT  0.00V MIN  0.00V
02:16:43.042 -> MAX PWM 1023.0 -1023.0
02:16:43.042 -> MAX VEL   0.03   0.01 m/s    4.04 rad/s
02:16:43.042 -> MIN VEL  -0.01  -0.01 m/s   -4.04 rad/s
02:16:43.042 -> MAX ACC   1.15   0.92 m/s2   85.77 rad/s2
02:16:43.042 -> MIN ACC  -1.15  -0.92 m/s2  -90.87 rad/s2
02:16:43.042 -> IMU ACC   5.06  -2.95 m/s2
02:16:43.042 -> time to 0.9x max vel   0.18 sec
02:16:43.042 -> distance to stop   0.15 rad
02:16:43.042 -> BAT  0.00V MIN  0.00V
02:16:47.420 -> MAX PWM  511.5 -511.5
02:16:47.420 -> MAX VEL   0.43   0.04 m/s    0.12 rad/s
02:16:47.420 -> MIN VEL  -0.42  -0.02 m/s   -0.06 rad/s
02:16:47.420 -> MAX ACC   8.50   1.15 m/s2    5.11 rad/s2
02:16:47.420 -> MIN ACC  -8.50  -1.15 m/s2   -4.08 rad/s2
02:16:47.420 -> IMU ACC   3.87  -3.95 m/s2
02:16:47.420 -> time to 0.9x max vel   0.26 sec
02:16:47.420 -> distance to stop   0.02 m
02:16:47.420 -> BAT  0.00V MIN  0.00V
02:16:51.767 -> MAX PWM  511.5 -511.5
02:16:51.767 -> MAX VEL   0.02   0.02 m/s    1.80 rad/s
02:16:51.767 -> MIN VEL  -0.03  -0.02 m/s   -1.78 rad/s
02:16:51.767 -> MAX ACC   1.15   0.92 m/s2   36.76 rad/s2
02:16:51.767 -> MIN ACC  -0.92  -1.15 m/s2  -38.80 rad/s2
02:16:51.767 -> IMU ACC   2.30  -2.45 m/s2
02:16:51.767 -> time to 0.9x max vel   0.12 sec
02:16:51.767 -> distance to stop   0.06 rad
02:16:51.767 -> BAT  0.00V MIN  0.00V
02:16:56.111 -> MAX PWM  511.5 -511.5
02:16:56.111 -> MAX VEL   0.43   0.04 m/s    0.12 rad/s
02:16:56.111 -> MIN VEL  -0.43  -0.02 m/s   -0.08 rad/s
02:16:56.111 -> MAX ACC   8.50   1.38 m/s2    5.11 rad/s2
02:16:56.111 -> MIN ACC  -8.50  -0.92 m/s2   -5.11 rad/s2
02:16:56.111 -> IMU ACC   3.83  -3.60 m/s2
02:16:56.111 -> time to 0.9x max vel   0.24 sec
02:16:56.111 -> distance to stop   0.02 m
02:16:56.111 -> BAT  0.00V MIN  0.00V
02:17:00.456 -> MAX PWM  511.5 -511.5
02:17:00.456 -> MAX VEL   0.02   0.01 m/s    1.80 rad/s
02:17:00.456 -> MIN VEL  -0.02  -0.02 m/s   -1.78 rad/s
02:17:00.456 -> MAX ACC   1.15   1.38 m/s2   37.78 rad/s2
02:17:00.456 -> MIN ACC  -0.92  -1.38 m/s2  -38.80 rad/s2
02:17:00.456 -> IMU ACC   2.07  -1.88 m/s2
02:17:00.456 -> time to 0.9x max vel   0.12 sec
02:17:00.456 -> distance to stop   0.06 rad
02:17:00.456 -> BAT  0.00V MIN  0.00V
02:17:04.827 -> MAX PWM  255.8 -255.8
02:17:04.827 -> MAX VEL   0.16   0.02 m/s    0.08 rad/s
02:17:04.827 -> MIN VEL  -0.17  -0.02 m/s   -0.06 rad/s
02:17:04.827 -> MAX ACC   3.22   0.92 m/s2    4.08 rad/s2
02:17:04.827 -> MIN ACC  -3.68  -0.92 m/s2   -4.08 rad/s2
02:17:04.827 -> IMU ACC   2.03  -2.99 m/s2
02:17:04.827 -> time to 0.9x max vel   0.30 sec
02:17:04.827 -> distance to stop   0.00 m
02:17:04.827 -> BAT  0.00V MIN  0.00V
02:17:09.172 -> MAX PWM  255.8 -255.8
02:17:09.172 -> MAX VEL   0.01   0.01 m/s    0.67 rad/s
02:17:09.172 -> MIN VEL  -0.02  -0.01 m/s   -0.61 rad/s
02:17:09.172 -> MAX ACC   0.69   0.69 m/s2   14.30 rad/s2
02:17:09.172 -> MIN ACC  -0.92  -0.92 m/s2  -15.31 rad/s2
02:17:09.172 -> IMU ACC   2.07  -0.92 m/s2
02:17:09.172 -> time to 0.9x max vel   0.16 sec
02:17:09.172 -> distance to stop   0.02 rad
02:17:09.172 -> BAT  0.00V MIN  0.00V
02:17:13.551 -> MAX PWM  255.8 -255.8
02:17:13.551 -> MAX VEL   0.16   0.02 m/s    0.08 rad/s
02:17:13.551 -> MIN VEL  -0.16  -0.01 m/s   -0.04 rad/s
02:17:13.551 -> MAX ACC   3.45   1.15 m/s2    3.06 rad/s2
02:17:13.551 -> MIN ACC  -3.45  -0.92 m/s2   -4.08 rad/s2
02:17:13.551 -> IMU ACC   2.41  -2.61 m/s2
02:17:13.551 -> time to 0.9x max vel   0.16 sec
02:17:13.551 -> distance to stop   0.00 m
02:17:13.551 -> BAT  0.00V MIN  0.00V
02:17:17.900 -> MAX PWM  255.8 -255.8
02:17:17.900 -> MAX VEL   0.02   0.01 m/s    0.65 rad/s
02:17:17.900 -> MIN VEL  -0.02  -0.02 m/s   -0.61 rad/s
02:17:17.900 -> MAX ACC   0.92   0.92 m/s2   13.27 rad/s2
02:17:17.900 -> MIN ACC  -0.69  -0.92 m/s2  -16.34 rad/s2
02:17:17.900 -> IMU ACC   1.07  -1.46 m/s2
02:17:17.900 -> time to 0.9x max vel   0.12 sec
02:17:17.900 -> distance to stop   0.02 rad
02:17:17.900 -> BAT  0.00V MIN  0.00V

An image of the robot while turning or rotating

Pattapol2005 Apr 18, 2025
Author

I modified the max_particles value in the navigation.yaml, and it worked when the robot rotates around the Z-axis. However, I'm not sure if this is the correct method.

PaulBouchier · 2025-05-28T18:24:39Z

PaulBouchier
May 28, 2025
Collaborator

Your problem could be that you're using a single-channel encoder. I assume you've got something like a yellow TT motor with a speed-sensing encoder (disk with slots & opto-sensor). Linorobot is intended to be used with quadrature encoders. You need to get a yellow TT motor with quadrature hall-effect encoders (FITj0450 from DFRobot works).

The problem with a discrepancy between measured RPM and RPM reported by test_motors could arise if you don't have interrupts enabled. You might be losing transitions.

1 reply

Pattapol2005 Jun 3, 2025
Author

Hello, I’m new to ROS and I have an additional question: if I modify the firmware to support a single-channel encoder, how much would Odometry or Kinematics be affected? Thank you.

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