Which electrical motor for self balancing robot project

[cineq]

Hi all,

I am going to build self balancing robot. I want to have construction gabarites similar to:

http://www.danielbauen.com/balancing_robot/images/balancing-robot.jpg

I have a question about electrical motors for weels, because I met a lot of different examples.
What will be the best choice? Stepped motor or DC? If DC, should it be brushless or not? Which parameters are the most important for this type of construction?


Regards M.

 

[Audioguru]

The brushless DC motors in my electric radio controlled model airplanes do not start running smoothly like a brushed DC motor does. The brushless DC motor frequently starts backwards for a moment then runs properly forward. It will make your robot stagger like a drunk person.
I do not know how to reverse the running direction of a brushless DC motor, for a brushed DC motor you simply reverse the polarity of the voltage.

But my brushless DC motors last forever and my brushed DC motors wear out soon and make sparks and interference.

 

[CncHobby]

There is information about motor source and others on their website:

http://www.danielbauen.com/balancing_robot/surplus.htm

The motor used is 12v geared dc motor.

 

[cineq]

There is information about motor source and others on their website:

http://www.danielbauen.com/balancing_robot/surplus.htm

Yes, I know that there are used 12V DC motors, but I am thinking if there is better choice. For balancing purposes it is important to have big torque near point ZERO of balance. The problem of brushed motors is that they have low torque at low speeds. Stepped motors have high torque regardless the speed, but also have big power drain... I am not sure what about brushless motors will work with this kind of project.

 

[CncHobby]

IMO, stepper motor with it's stepping nature would not good for self balancing robot, bldc can be good but the driver complexity will go up significantly.

 

[chuckey]

Brushed DC motors is the way to go. They exhibit constant torque at a constant current at any speed, including zero RPM. If you can get them, a series wound type is the best (like a car starter motor), because at zero speed the current is enormous, so both the field and rotor magnetic field are high, so the starting torque is high, but a magnet powered field is a good second best.
A BLDC motor is essentially a fixed speed device unless you take it apart and and build your own drive circuit. They will have six "dead" spots over one revolution, which is why their starting is problematic.
A stepper motor could be a good choice, though it will have N dead spots, causing it to "cog" at zero speeds. They are significantly more expensive and their drive circuitry is far more complex. They are also much bigger then DC motors.
I do not know exactly what the machine is going to do, but the one shown in the pic, looks wrong. Its called the moment of inertia, the machine should not be tall, it should be as low as possible built fore and aft, slung UNDER the axle, this makes it more stable. Think of a tightrope walker he carries his pole horizontally not vertically.
Frank

 

[Audioguru]

I would think that a self-balancing robot must begin leaning towards the direction it needs to go. If it wants to go forward then it should begin leaning forward. How to make it lean forward? Simply run it for a moment in reverse. The inertia of the top parts will cause it to lean forward. Then it can burn rubber like crazy as it accellerates!