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Topic: Arduino and balancing brushless Motor controlled unicycle? (Read 976 times) previous topic - next topic

deankamen

May 18, 2012, 10:27 pm Last Edit: May 18, 2012, 11:26 pm by deankamen Reason: 1
Hello
This is my first post, I have been lurking on this site as a guest for a while, and wanted some insight on how exactly to go about this process.

I would like to replicate this brushless unicycle.
http://www.youtube.com/watch?NR=1&feature=endscreen&v=SBONp01U7Fk

I have been inspired by this project to build a DiY version, and would greatly appreciate the help along the way. I have some of the parts for this project, namely,
1) brushless motor
2) ebike controller
3) arduino mega

seeking to buy 3-axis of freedom gyroscope

I am struggling to figure out how to control the 0-5k resistor throttle using the arduino
or
variating the 0-5v hall effect sensor, and mimicking the output accordingly

I put my meter in current mode and the the current is 0.5mA, which makes sense if there's an internal 10kohm pull up resistor to 5v.

I dug out an old 5kohm pot and put it across the controller end of the cable. With the pot across red and yellow, with the wiper on blue, the motor runs fine, and the voltage sense is still backwards. High voltage is stopped, low voltage runs fast. The odd thing is that there's only a 0.5 volt range from stop to full speed; and it's offset, too. Specifically, 3.0 volts is full speed, and 3.5 volts is full stop. Very narrow range. This is with the wheel off the ground though -- maybe it has a wider voltage swing under load.
There is a reverse on the controller, that I have hard-wired, adding a fourth wire to the 3-wire throttle. (one is +, other is -, and one is neutral)
so four cables

Could this be interfaced similarly to a stepper motor?
Is it more similar to running a servo motor?

I've concluded that, shorting the the sense wire input to gnd runs the motor at full forward speed, shorting the reverse runs the motor at 40% power.


Please let me know of any tips to interface a brushless motor controller to an arduino
many thanks

Dean

MarkT

Motor controllers for vehicles like eBikes and wheelchairs are often deliberately restricted in acceleration to give a smooth ride.
such ones won't be able to react fast enough to maintain balance - you want maximum torque in a short space of time, any delay will reduce the effectiveness of the PID control loop.

[ Incidentally this is the wrong forum, there is a forum for motors ]

You will need at least a 1-axis gyro and 2-axis accelerometer to detect rotation rate and tilt - MEMS gyros are rate gyros with a lot of drift, good only for the short term correction.  The average tilt from the accelerometer is used to correct the drift - you'll want to place the accelerometer close to the axle for best response - you want it to experience tilt only.

You'll need a motor controller that has fast response and drives 100% in either direction, and a sensored BLDC.  You might find a brushed motor and controller both easier to find and cheaper though.

[ I won't respond to messages, use the forum please ]

deankamen

I have found a high torque, high power BLDC, and found a high power BLDC motor.
The only problem I have is getting the arduino to function properly.
hrm. I think All that's left now is the coding, to get it to balance....

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