Science Most Powerful DC Motor

[Bonanza123d]

Hey All,

I need to find a motor for a robotics project that can has a lot of torque, and a lot of speed at the same time. It also can not be over 2 inches in diamater.

 

[Quick_Nick]

CIM motors are used extensively for FIRST robotics.
But they are 2.5" diameter. And it turns out the Mini CIM is the same diameter.
But I found a similar product here that ought to be just right: http://www.vexrobotics.com/vexpro/motor-controllers/217-3351.html
If this doesn't have enough speed and torque under 2", I don't know what would.

 

[tl8]

Hey All,

I need to find a motor for a robotics project that can has a lot of torque, and a lot of speed at the same time. It also can not be over 2 inches in diamater.

Brushless motors are going to be your best bet. However you need additional electronics to run them properly. Have a look at Sparkfun. They might have what you need.

 

[RisingFury]

How much RPM? If you're looking at high torque and RPM in the thousands, you should look into RC car motors. But you'll need additional electronics for it: Speed control, which takes a PWM signal (you can create it, I created it using an Arduino for my servos or you can use a transmitter / receiver) and a LiPo battery.

 

[Bonanza123d]

How much RPM? If you're looking at high torque and RPM in the thousands, you should look into RC car motors. But you'll need additional electronics for it: Speed control, which takes a PWM signal (you can create it, I created it using an Arduino for my servos or you can use a transmitter / receiver) and a LiPo battery.

I need a motor that can be computer controlled, Has 200 lb/in torque, and 7000 rpm. Is this asking for a little too much? I need it for a force feedback system.

 

[Quick_Nick]

I need a motor that can be computer controlled, Has 200 lb/in torque, and 7000 rpm. Is this asking for a little too much? I need it for a force feedback system.

Whether it's too much depends on your budget. (I don't know about that torque though, for the size and all)

Are you planning to have your PC as the brain of the robot or will/does it have anything onboard already like Arduino, cRIO, etc. I don't know the scale of this project.

 

[Bonanza123d]

Whether it's too much depends on your budget. (I don't know about that torque though, for the size and all)

Are you planning to have your PC as the brain of the robot or will/does it have anything onboard already like Arduino, cRIO, etc. I don't know the scale of this project.

The scale requirement will be massive, because i will need around 30+ motors, all with varying strength. I will need for them to be fairly cheap. I will also temporarily have a small laptop running Ubuntu with the control software. Also i will need motors that do not overheat if the object's force is too large for the motor.

 

[Artlav]

Am i the only one who read the thread title, and thought www.youtube.com/watch?v=3pjIpVXZyPo#t=40s ?

On topic, what would the motors do?
Do these 7000RPM spin in circles, or only used to quickly rotate a joint within one circle?
In the last case, look for servo motors, although 200lb/in sounds like too much for RC shop stuff.
If i got the units translated correctly, that's multi-kilowatt range motor.

Force feedback sounds like the latter, and is done with servos (steering wheel) or pneumatics (chair)/hydraulics (cockpit).

 

[Bonanza123d]

Am i the only one who read the thread title, and thought www.youtube.com/watch?v=3pjIpVXZyPo#t=40s ?

On topic, what would the motors do?
Do these 7000RPM spin in circles, or only used to quickly rotate a joint within one circle?
In the last case, look for servo motors, although 200lb/in sounds like too much for RC shop stuff.
If i got the units translated correctly, that's multi-kilowatt range motor.

Force feedback sounds like the latter, and is done with servos (steering wheel) or pneumatics (chair)/hydraulics (cockpit).

I am going to be running a C3P0 like design for joint control with strings. I want to have high torque and high speed for rotation. Also the motor needs to be 2 inches in diameter.

 

[Quick_Nick]

On topic, what would the motors do?
Do these 7000RPM spin in circles, or only used to quickly rotate a joint within one circle?
In the last case, look for servo motors, although 200lb/in sounds like too much for RC shop stuff.
If i got the units translated correctly, that's multi-kilowatt range motor.

Force feedback sounds like the latter, and is done with servos (steering wheel) or pneumatics (chair)/hydraulics (cockpit).

I'm not good with this math, but scanning Wikipedia and plugging into WolframAlpha, I get 104kW or 140hp for 200 in-lb and 7000rpm simultaneously. Of course, he probably wants 200 in-lb stall torque, in which case I'm really not sure what math to use. But I still don't know where to get that kind of power and how that can be applied to a small motor. Our CIMs got really hot after minutes of use, and that was just 12V and 1/10 the stall torque.

The scale requirement will be massive, because i will need around 30+ motors, all with varying strength. I will need for them to be fairly cheap. I will also temporarily have a small laptop running Ubuntu with the control software. Also i will need motors that do not overheat if the object's force is too large for the motor.

I can't help with any of that! Definitely too complex for me. I don't even know a particular controller for 30 independent motors. Muchless anything 'cheap' depending what that means.
And along with the apparent massive power requirement of just one motor... You might have to contact the utility company about running 30 of these. :lol:

 

[Bonanza123d]

I'm not good with this math, but scanning Wikipedia and plugging into WolframAlpha, I get 104kW or 140hp for 200 in-lb and 7000rpm simultaneously. Of course, he probably wants 200 in-lb stall torque, in which case I'm really not sure what math to use. But I still don't know where to get that kind of power and how that can be applied to a small motor. Our CIMs got really hot after minutes of use, and that was just 12V and 1/10 the stall torque.



I can't help with any of that! Definitely too complex for me. I don't even know a particular controller for 30 independent motors. Muchless anything 'cheap' depending what that means.
And along with the apparent massive power requirement of just one motor... You might have to contact the utility company about running 30 of these. :lol:

I will not be running every motor at the same time, but they will all be variable voltage and power control depending on what the computer tells it.

 

[Artlav]

Controlling should be easy, if you use servos. Ones from RC shop are controlled by a PWM signal.

Meaning you can get a bunch of little general-purpose microcontrollers like attiny25 and hook up 3-4 motors to each.
Then, wire the MCs together with a bus like I2C, and hook the bus up to a computer/Arduino/whatever.
Quite easy to scale to any number of motors (within the bus bandwidth/address space).

Here is an example with my hexapod wired this way - 18 motors, 3 per leg, one attiny chip controlling every leg, one big MC core controlling the tinys.
It's not too good at traction yet, but is quite good at making leg movements.

 

[RisingFury]

I need a motor that can be computer controlled, Has 200 lb/in torque, and 7000 rpm. Is this asking for a little too much? I need it for a force feedback system.

Yes, it's a lot too much to ask for!


If you want high torque, definitely go for servos. But don't expect them cheap. They high torque and high speed servos are in the 100 to 200 $ range. You can expect torque in the range of 100 to 200 N*cm (that's a lot, trust me) and a rotation speed of about 0.1s / 60° to 0.2s / 60° (that's very fast). That's for 6 volts. With 4.8, the specs drop a bit.

Such high torque servos are usually used for very large RC planes (upwards of 4 to 5 meter wingspan) or for RC sail boats - specifically, the servos controlling the sail have to be fast and have high torque.


Servos can be analog or digital. Both take PWM signal to operate, which is easy to create using a microcontroller. The difference is that analog servos take a PWM signal in the frequency of about 30 to 50 Hz, but the digital ones are capable of 400 Hz or more.

The biggest difference is in torque. Go for the digital ones, because with 400 updates per second, you'll have more effective torque.

The analog servos won't really work with the 400 Hz update rate. You can push them a bit beyond 50, but at about 100 they just start making a high pitch buzz, because the electronics is no longer capable of such high refresh rate. They don't really break down, they just don't act the same way you'd expect them to.


There's another thing to look for: Some servos are limited as far as their rotation goes. They can rotate from about -100° to about +100°. Others have a free rotational range. They can spin around freely. The RC sailboats use the free spinning ones for the sail sometimes, depending on the design, while just about everything in RC planes is limited to +-100°. In fact, most of the time, you don't even make use of the full 100°.


Avoid cheap servos. You can get cheap Turnigy servos that claim to have the same specs as stuff from Futaba or Graupner, but they have a higher failure rate. Also, certain servos don't have a diode that protects against applying wrong voltage polarity. Inverting the polarity (yea, yea, laugh it up) fries the servo, if it has no protection. (So remember, kids, always use protection!)

 

[Bonanza123d]

well, looks like i am going for the free turning servos. I need the power. I also estimated that i will need 40 motors running on all different systems for it to work properly, also connect to a computer. Can someone point me in the correct direction for PCB (Printed Circuit Board) parts and design?

Thanks