Dear All,
Have a nice day
I am making a robot arm it has three axis
I want to check the what angle each axis is ,which i can limit the rotation
Edit : We need to control this arm using drone transmitter
Please advice best angle sensor that I can use
Following can not be used
Limit sensor
Compass
Rotary encoder
Variable resistor
image of robot
Please advice
Thanks in advanced
Why the restrictions on what can be used ?
PA3040:
Following can not be used
Limit sensor
Compass
Rotary encoder
Variable resistor
Why?
The picture isn't very clear. What model robot arm kit are you using?
If you are using stepper motors to move the arm segments then if you have a suitable homing sequence for each of the you can accurately identify the angle from the number of steps that you command the motor to move. No need for any external measurement.
...R
Robin2:
if you have a suitable homing sequence
I wonder if "home sensors" are as forbidden as "limit sensors".
johnwasser:
I wonder if "home sensors" are as forbidden as "limit sensors".
Oops! I mis-read the Original Post. I thought it was a list of the things that could be used.
If the mechanical framework is strong enough it would be possible to HOME the motors by driving them beyond their limit so that they miss steps.
...R
Robin2:
If the mechanical framework is strong enough it would be possible to HOME the motors by driving them beyond their limit so that they miss steps....R
I love that idea.
Teacher: "Why does it make that horrible grinding noise every time you power it up?"
Student: "That's what happens when you forbid limit switches and absolute encoders."
Can anyone read the brand name in that fuzzy picture? I can find plenty of very similar robot arms with Google but not that exact model.
Here's one.
Grab two pieces of polaroid plastic. One on each side of the rotating joint. Shine an LED through them and measure the amount of light passed through as they rotate around each other.
-jim lee
Due to the unexplained restrictions, I assume this is a class assignment. You might only need an attractive dancer from the local gentlemen's club you can train to take position measurements for you, and a law student to explain to the instructor that dancers were not excluded.
johnwasser:
I love that idea.
Teacher: "Why does it make that horrible grinding noise every time you power it up?"
Student: "That's what happens when you forbid limit switches and absolute encoders."
Can anyone read the brand name in that fuzzy picture? I can find plenty of very similar robot arms with Google but not that exact model.
it is called dobot robot ( old version )
Robin2:
If you are using stepper motors to move the arm segments then if you have a suitable homing sequence for each of the you can accurately identify the angle from the number of steps that you command the motor to move. No need for any external measurement....R
Dear Robot2
I am sorry that i could not mention that Edit : We need to control this arm using drone transmitter
Dear All
Limitation due to non mechanical and compass added by me since it is impossible to apply in this case
There is a slim chance to use rotary encoder but I think it can not keep remember last angle when power
up,
Is there any angle sensor that i can apply
Just use a Pot. It remembers its position.
-jim lee
PA3040:
Is there any angle sensor that i can apply
Absolute encoder.
"I want to check the what angle each axis is ,which i can limit the rotation
Edit : We need to control this arm using drone transmitter"
Does this new requirement provide for two way data transmission? Anything prevent you from standing next to the arm with the transmitter and just watch the arm to see its position? Just call it optical position determination. You keep coming up with new bounding conditions, so what else have you not mentioned?
PA3040:
Dear Robot2I am sorry that i could not mention that Edit : We need to control this arm using drone transmitter
I am not a Robot !
The statement I have quoted here does not in any way preclude identifying the angle by keeping count of the steps.
If you have a mechanical design using stepper motors that cannot accommodate some form of limit switch then you need to revise the mechanical design.
If you want a two-way wireless control system then the simple solution is to use a pair of nRF24L01+ transceiver modules. They work very well and I use them for controlling model trains with the train sending back data on battery voltage to the controller. Have a look at this Simple nRF24L01+ Tutorial.
...R
The KickStarter for the 'dobot' shows encoders on the steppers. Were those not included wit your model?
The project is supposed to be "open source" and "Arduino compatible" but I can't find the firmware sources at the dobot.cc site.
johnwasser:
The KickStarter for the 'dobot' shows encoders on the steppers. Were those not included wit your model?The project is supposed to be "open source" and "Arduino compatible" but I can't find the firmware sources at the dobot.cc site.
I asked from dobor cc , they have replied
PA3040:
I asked from dobor cc , they have replied
https://forum.dobot.cc/t/dobot-position-sensor/3538/2
The large and small arms have angle sensors, and the limit is automatically calculated according to the angle and the software-defined range. The base is a code wheel, read the position of the code wheel and the defined limit value to limit.
Well that's good. Now you just need the documentation for the existing sensors.