Hello Folks,

I want to measure object geometrical position very accurately. Okay let me explain my problem in detail.
I have a robot, which I want to move from a particular position to another position, the distance between two positions is very small max 160 cm. The movement is angular and bidirectional.. Like below.


To detect the geometrical position I have been used IMU sensor and placed vertical with ground and It is working but not accurate. The logic is At the first time I am taking yaw values of both position and saves it on EEPROM(calibration). Next when Robots starts from the position1 then it continuously checking position2 yaw value when its match with that its stopped moving. But, the problem is it is not stopping exactly same position, there always error +-5cm. I have tried many way to correct the error but it not worked, I observed that while moving the motor it unable to measure correct IMU value even the static IMU value also changing by time. These two position is not fixed for all time after few time position needs to change as per application.


So, I am looking for a solution by which I can measure the position very accurately. Please let me know any other proven solution available by which I can measure position accurately. Thank you.

 

There is an article, which I am looking for, which uses two modified Ping! sensors to triangulate and objects position. Basically, the ultrasound transmitter of one is disabled. The receiver on that module will respond to the transmitter of the other module. The difference in response times between the two sensors and the distance between them are used to calculate the location of the sensed object.

I’ll keep looking...

 

Here is the article...

And here is a build article using a compatible sensor but not in this application.

You might also be able to put the sensor on a rotating platform, and scan the area for the object. I’m trying this approach in another project.

 

Does this robot have sensors on every motion axis servo? If it does they should be able to provide adequate position sensing far more accurately, and use the other sensor for path control. Typical accuracy of the robots that I have programmed was at worst +/-0.5mm, far better than 5cm variation. But ultrasonic sensors are never as accurate, especially when the object is moving.

 

Does this robot have sensors on every motion axis servo? If it does they should be able to provide adequate position sensing far more accurately, and use the other sensor for path control. Typical accuracy of the robots that I have programmed was at worst +/-0.5mm, far better than 5cm variation. But ultrasonic sensors are never as accurate, especially when the object is moving.

Thank you for your reply.
No, it doesn't have any motion axis sensor. Please tell me about it in detail. Thank you.

 

Here is the article...

And here is a build article using a compatible sensor but not in this application.

You might also be able to put the sensor on a rotating platform, and scan the area for the object. I’m trying this approach in another project.

Thanks for your suggestion. We have tried this way before IMU. Accuracy was worse than IMU. Please suggest any other option.

 

In some robots there is an encoder on the drive motor for each axis, and this provides feedback so that the control system can know where each axis is all the time. How do the axis drives in your robot provide feedback to their controllers? If there is no feedback then it is not really a robot.