Hot answers tagged

30 votes
Accepted

Robot never goes straight

I'm posting this as an answer because it is the answer. You can't. As @BendingUnit22 mentions, you are attempting "open loop" control. Noise and variations will mean that your robot will never ...
user avatar
  • 14.7k
10 votes
Accepted

How is a brushless gimbal motor different from a regular brushless motor?

I believe this blog has at least part of the answer to your question. Brushless gimbal motor vs. Brushless Motor vs. Servo A user here described the comparison as: A brushless gimbal motor is a ...
user avatar
  • 251
9 votes
Accepted

Simple equation to calculate needed motor torque

How quickly do you want to go from stopped to 10rpm? This will define your angular acceleration. Regarding calculations, first you should convert to standard units, so meters instead of centimeters ...
user avatar
  • 14.7k
8 votes
Accepted

Calculating Required Torque

This is a standard dynamics problem. Let's use this figure I drew: Some definitions: $$ \begin{align} m & \mbox{, the mass of the vehicle in kg.} \\ \mu_{\mbox{rolling}} & \mbox{, the ...
user avatar
  • 14.7k
7 votes
Accepted

For robot wheel control : Brushless DC motor or Servo Motor?

Let's try and clear things up a little bit... "RC Servo" motors These can be found in radio controlled cars and airplanes to e.g. turn the wheel or actuate various controls in the airplane. They ...
user avatar
  • 1,080
7 votes

How high of a gear ratio can a motor have?

Your calculation of about 80 N⋅m torque for lifting 8 kg with a 1 m lever arm is ok; more precisely, the number is 8 kg ⋅ 9.81 m/s² ⋅ 1 m = 78.48 N⋅m. As mentioned in other answers, you will need to ...
user avatar
7 votes

Motor Choice given size constraint and load requirement

If you have some budget for your project, both Maxon and Faulhaber have good DC motors and motor-gearhead combinations. Maxon publishes a nice set of formulas and background theory on electric motors....
user avatar
  • 4,225
7 votes
Accepted

Harmonic drives in hobby projects

The core reason for choosing harmonic drives is desire for zero backlash. Moreover, regarding mass and size, they become more beneficial for higher gear ratios as their size and mass do not scale for ...
user avatar
7 votes
Accepted

Using brushless motors for very high torque

Your expectations are rather aggressive for a DC motor. First - 40Nm (350in-lbs) is A LOT of torque! Ex: A max rated torque for 1/4-20 bolt is only 75 in-lb (8.5Nm). Second - The mechanical power ...
user avatar
6 votes

What is stall current and free current of motors?

All very good answers, but as a physics teacher I am concerned about some incorrect equivalences here that can only lead to confusion. One form of [energy][1], eg [chemical potential energy][2], can ...
user avatar
6 votes
Accepted

Passing power through a motor

It is called a slip ring. It works the same as a brushed motor. See here for a robotic oriented one. Larger versions handle power, and cost more. Also near field technologies such as those used to ...
user avatar
  • 2,013
6 votes

Robot never goes straight

Since the open-closed loop issue is already mentioned, I will give a comment to the "I once tried to run a dc-motor without a load". Yes you might damage your motor with this but you can also damage ...
user avatar
  • 1,647
6 votes

Motor Choice given size constraint and load requirement

20kg is a mass. It makes a force on Earth (20*9.81 = 196N), but that's not a torque. Motors make torque - what is your maximum torque specification? Once you know how much torque you need (that will ...
user avatar
  • 14.7k
6 votes

What are some ways to estimate torque/load on a robotic arm joint

Model Based: Low cost solution is always software: Develop a dynamic model which computes the load on the motors based on the motions (e.g. with Recursive Newton Euler Algorithm or Lagrange-Euler ...
user avatar
  • 6,412
6 votes
Accepted

What is the difference between DC motor with encoder and DC with out encoder?

As @szczepan mentions, the difference is one of feedback. There are many ways to get feedback regarding the motion of a dc motor. People implementing a control system will often put a mark on the ...
user avatar
  • 4,326
5 votes

How to convert vertical motion to horizontal?

Scott-Russell type mechanism. For weeks I was trying to come up with a solution for that exact problem for a engineering project mine. Look it up.
user avatar
5 votes

What mechanical parts can be attached to DYJ48 stepper motor?

You can drill a hole to match the shaft into whatever it is and either fix it with a setscrew against the flat or glue it. Or you could glue a brass tube (hobby shop) to the shaft if you can find one ...
user avatar
5 votes
Accepted

DC motor control - speed-torque curve

The problem is that you cannot control both the voltage and the current. You apply a voltage, and the motor draws whatever current it wants (subject to your ability to supply that current). ...
user avatar
  • 6,337
5 votes
Accepted

Continous rotation with cables

There is also ready to use commercial solution from Adafruit, called "slip ring" http://www.adafruit.com/products/736 The only problem is the max speed, which is only 300rpm, but probably you won't ...
user avatar
  • 953
5 votes
Accepted

Length and Width of a Line Following Robot

Actually, the caster wheel has ideally no effect on the kinematics of the vehicle. In reality there will be some resistance from the caster wheel that does impact the vehicle motion, but we can still ...
user avatar
  • 1,357
5 votes
Accepted

Quadrature encoder signal from dc motor is very noisy

Conceptually everything was set up correctly, but a number of basic mistakes affected the signal. Here is the set-up which should be used to record the signal from one of the encoder outputs: A set ...
user avatar
  • 233
5 votes
Accepted

Why to combine a Raspberry Pi (or similar board computer) and an Arduino for controlling motors?

The reason is Clock on the Raspberry Pi. Note that the raspberry is powerful but not that powerful that it can run an OS and simultaneously give you precisely timed PWM outputs. I assume that you'll ...
user avatar
5 votes
Accepted

How much weight can DC Motor carry?

Well, to answer this question for your special case, one needs more information about the motors. Maybe, you can supply a product code. And one needs more details of the involved mechanics... is it a ...
user avatar
  • 271
5 votes

Equations of motion in matrix form and energy consumption

Can you set up the problem so that the quantities you care about (e.g. power) are more explicitly represented? Reasoning physically, where could the power go? Accelerating masses, including rotation ...
user avatar
  • 1,136
5 votes

What kind of motors do industrial robot have?

Most industrial robot have servo motors. This allows you to control velocity, torque and position of motors - the latter usually in some form of closed-loop control system. I work for Stäubli. Our ...
user avatar
  • 249
4 votes

Choosing motor for a tricopter

This depends on what you want to do with your copter. Hovering: 100-150 Watt/kg ScaleFlight: 200-300 Watt/kg Some chilling acrobatic flight: ...
user avatar
  • 1,647
4 votes
Accepted

Rotate (and stop) a large disk in very tiny increments

You can use stepper motors easily: Given the 20cm diameter, this is around 63cm circumfence. Your target stepsize is around 0,1mm. This means the motor should do around 6300 steps per revolution. If ...
user avatar
  • 1,647
4 votes
Accepted

Submarine screw and the isolation from the water

A variety of techniques are used for propeller shaft sealing. One of the most common is a "packing gland" or "stuffing box", as in illustration below from a dieselduck.info web page which has details ...
user avatar
4 votes
Accepted

Robotic winch force sensor

There are two ways that I can think of measuring this: Motor current, as the resistance to motion increases the current increases linearly, you could measure the desired torque and the current and ...
user avatar
  • 1,909

Only top scored, non community-wiki answers of a minimum length are eligible