# Tag Info

11

In a nutshell, servo motors and stepper motors are not technically the same things. The link you posted is only for servos and not stepper motors. A servo motor assembly does not rotate freely like a DC motor. The rotation angles are usually limited, and every servo has a "lock" position where it stays by default. A positive pulse makes it move clockwise, ...

7

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 of a motor results from RPM*Torque. 40Nm*100rpm is 0.56hp (420W at 100% efficiency). That is A LOT, about 1/2 of what today's high end cordless drills can do. ...

6

The short answer is yes, but the long answer is that you're approaching the code the wrong way and will need to rewrite things a bit. It looks like you're attempting to read a button and have it flash some LEDs while at the same time having your stepper move back and forth. The problem is your delay(5); commands, which pause the execution of your code. ...

6

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 wirelessly charge your electric toothbrush, and more recent wireless cell phone chargers, are potential solutions

5

If you want to detect missed steps, you want an encoder. Luckily, both magnetic and optical encoders exist that easily give you 4096 steps per revolution, so even a micro-stepping stepper motor will be measured with at least one step per step. Note that some CNC mills may not necessarily detect missed steps; it's up to the operator to not program a tool ...

5

Whether a motor can spin continuously depends how is is constrained by other parts of the system. An rc servo like the MG995 will typically have a motor, a gearbox and a limited travel potentiometer to provide position feedback. It is this final component which prevents the rc-servo from rotating continuously. In the case of the MG995, it can apparently be ...

5

There are 2 (or 3, depending on how the planned lifetime of the robot is) thing thats you have to consider. Static load: The motors stall (zero revolution) torques have to be able to hold the weight in the robots most unfavorable pose (usually the arm stretched out). You can determine this by static modelling, that involves only an equilibrium of forces for ...

5

You will find it helpful to keep the physical robot and the math separate. The kinematics equations map joint parameters (which are often grouped as a vector $q$) to Cartesian coordinates ($x$,$y$,$z$). If you take the first-order partial derivative of the kinematics equations, you get a set of equations that map a change in the joint parameters to a ...

4

The ONLY difference between a stepper and a servo is that a Servo monitors its position with an encoder, and may increase power if it gets behind, or reduce power if it gets ahead, or generates a 'fault' condition if it is unable to move to the proper position in a predetermined time frame. There is no difference in power requirements. Any stepper can be a ...

4

I found that the FFT of the current waveform of the stepper often shows the natural frequency harmonics of the motor+driver system AND that during a stall extra frequency harmonics appear!!! all you need is a fast, bidirectional current to voltage conversion IC and a narrow band pass filter to detect if the extra harmonics are present.

4

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 you take a common stepper motor, which has a step size of around 1,8° per step. So the motor performs 200steps/per revolution. your target is 6300. Now we know ...

4

I have used MicroMo's stepper motors in the past. You can find their information here: http://www.micromo.com/products/stepper-motors/stepper-motors-datasheets However, I don't know if a design process of "make decisions then see what fits" is the best approach. You should determine the performance you need, then look for components, and base your ...

4

The S-Curve profile can have several divisions along the time axis 7 divisions as per this image. This example has a constant positive jerk zone, a constant acceleration zone, a constant negative jerk zone, a zero acceleration zone and then the vice-versa. This is the S-Curve in its most general form 5 divisions if there exists no constant acceleration ...

3

From wikipedia http://en.wikipedia.org/wiki/Stepper_motor Because windings are better utilized, they are more powerful than a unipolar motor of the same weight. This is due to the physical space occupied by the windings. A unipolar motor has twice the amount of wire in the same space, but only half used at any point in time, hence is 50% efficient (or ...

3

You need to quantify : "I measured the current through (one of the 4 wires of) my stepper motor, and it's always within a few percent of 0.5 A". A 'few percent' may be all you need to detect a little extra current during stall (if there is extra current as I would also assume but would need to prove), which can be sensed and compared to normal stepping ...

3

For this task; increase speed when a certain distance is reached. I would use encoders on the wheels which will workout the distance travelled and when the target distance is reached then increase speed.

3

Don't worry about the cables; plan to make them yourself. I recommend using one of the wide variety of crimp-on connectors available to you, depending on what you can find for your ESC and steppers connections. Here are a handful of connectors representing part of what we stock in our lab: The white connector is the Molex Minifit, the black one to its ...

3

I have never seen a stepper motor manufacturer not specify the torque vs. speed. I'm not sure where you've looked but a lot of people re-sell various random equipment to hobbyists without providing the same level of information. These graphs look like this one (source) The way you drive steppers has a large influence on their performance. The DC bus ...

3

Stepper motors are nasty little beasts and I don't like them. Actually, stepper motors are perfectly good as far as they go, but there are subtleties involved in selecting them and running them -- and I've had a couple of projects where the incorrect motor was chosen, then the problem of driving it was dumped unceremoniously in my lap. Given a stepper ...

3

Yes, general question. Here's some general bits-o-answer: some assembly is required. First, I would leave the decision about stepper vs. some other kind of motor until later -- it should be a tactical, not a strategic, decision. Second, assuming that the positive displacement idea works at all, I would assume that at the core of your machine you still ...

3

Holding torque, by the stepper motor definition, is not a valid way to quantify servo performance. Stepper motor torque drops off with speed whereas in a servo it remains relatively constant. (Operating torque is never half of holding torque and is RPM dependent, your guide lied to you). A real servo will always have a torque (continuous/operating) rating ...

3

I was hoping that someone else would answer this question with some sort of formula or rule of thumb that would apply to a much wider range of materials / cutting speeds / etc. According to the RepRap website, "It is recommended that you get approximately 13.7 N-cm (= 0.137 N-m or 1400 gf-cm or 19.4 ozf-in or 1.21 lbf-in) of holding torque (or more) for ...

3

Simple X-Y stages are well understood and form the basis for the many open source hardware projects for 3D printers. Each axis of an XY stage can be made from a pair of 6mm stainless steel rods, three LM6UU 6mm Linear Ball Bearings, a stepper motor (typically a NEMA14/17/23 motor) and stepper driver electronics. These axes can then be connected to the ...

3

You won't ever get 'exactly' 2042.8878 RPM, so going with your measurement accuracy I will assume you mean 2042.8878 +/- 0.0005 RPM. This is approximately an error of 1 part in 4 million. So let's assume you can set up a timer which counts up to around 4 million and resets, and use that for the PWM. Assuming a two pole motor, 2042 RPM is 34 electrical ...

3

At a guess this is either a Hall Effect, or Optical, speed and direction measurement device. The five wires will be GND, and outputs of Sensor1 and Sensor 2, and the other two would be the power supply to the Hall Effect/Optical Sensor (with there being a separate Vcc or GND for the power). This is a basic schematic for a Hall Effect based device This is a ...

3

This type of question "how much torque does my robot arm need" has been answered many times on this site: Simple equation to calculate needed motor torque Design and construction of universal robotic arm (5kg, 1m) Getting started with robotic arm design Choice of a motor for robotic arm The equation for torque is pretty simple. It is just force times ...

3

Servo mechanisms are not the "popular" RC-Servos (not-only). Servo is a closed-loop control, not only for motors. Even Steppers could or not be servo-motors. RC-servos are in major cases a DC brushed motor, with reduction gear and a potentiometer for position feedback, and electronic control. This is a common RC Servo. The fact that it has no ball bearings ...

3

Every action has an equal and opposite reaction. Each motor/joint in a linear chain of actuators (snake) needs to be capable of supplying the appropriate reaction forces. This mean that, if you have a 100cm long snake robot with a motor every 10cm, the first/"neck" joint (at 10cm) needs to support 8 other motors and 90cm of snake body. The second joint ...

3

When looking for motors, you usually are trying to figure out specific things with specific requirements. Holding Torque Torque at Speed Resolution (for steppers) NEMA size Positional Accuracy vs speed vs torque Movement Profile Budget So we need a little more info about your system. You're dealing with a 10kg load and your linear vel. is very slow at 0....

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