While less prevalent in step motor control ICs, active damping circuitry is common in off-the-shelf step motor drives. When properly applied, they can dramatically reduce the problem of ringing and therefore reduce noise and mid-range instability. In connection with electronic damping it's also important to mention the subject of current control, which we will cover in detail a bit later. Because of their high inductance, step motors are inefficient if the current flowing through their coils is not actively controlled.
This technique, called current control, is common in motion control and applies to servo motors as well. Motion control vendors don't always explain their current control technology separately from their anti-resonance technology, but the important point is that it is the net sum of how these two techniques perform that matter. Ultimately the proof is in the pudding, so you should look past fancy brand names and experiment with different controllers in your application to determine which one works best.
Before we go overboard on upgrades to the control scheme, we shouldn't forget that all step motors are not created equal, and that the choice of step motor type affects noise and vibration as well. Some motors, for example, have step sizes and configurations other than the industry standard 1. More phases mean smaller step sizes, potentially creating smoother motion. However, more phases also means the electronics will be more complicated and therefore more expensive. Another purely mechanical approach to consider is dampers.
These handy devices can reduce noise significantly and can reduce vibration to some extent as well. Figure 5 shows a typical step motor damper. Generally made of an elastomeric compound, they are installed between the motor and the load and do their job by introducing flexibility in the linkage of the two.
The negative for these devices is that they add compliance, which can complicate your system's motion dynamics and reduce the end positioning accuracy. While all the above mechanical options have their place, they have their drawbacks and it may be the case that their best days are behind them.
Compared to twenty years ago, when sophisticated controls were quite expensive, today that is anything but true. Today, so much can be done with the controls to reduce noise, and at a very modest cost, that interest in higher phase step motors and mechanical dampers is probably waning. Before moving on from this topic though, it is worth mentioning that properly sizing the motor for your application never goes out of style. So, plan on talking to your motor vendor so they can recommend the most suitable motor.
Don't forget to tell them the max torque needed, the operating speed range, and the inertia of the load. Particularly in a direct drive setup, step motors operate more smoothly and more quietly when the motor is well matched in particular, not overrated to the load. As Figure 6 shows, a microstepping waveform goes far beyond full step or half step and essentially drives the motor with sinusoidal waveforms.
The number of microsteps per full step is often programmable, and in high end controllers microstep counts of 64 or even microsteps per full steps are the norm. Beyond just changing the waveform, microstepping has another major effect on the control system which is that the addressable resolution is increased. For example, in a full step scheme with a 1. Is the addressable resolution equal to the actual accuracy?
Going back to our magnetic step motor model diagram, the actual position of the settled rotor is the sum of the internal equilibrium-restoring force and whatever external forces may exist on the rotor.
Therefore, in a given application, or for a given load, the exact actual profile path will vary a little bit from the theoretical commanded position. The most dramatic effect of implementing a microstepping control scheme is the reduction in noise and vibration, and therefore also a reduction in mid-range instability.
When first introduced, microstepping was a real breakthrough and helped breathe new life into the step motor marketplace. Today it is a common feature even in relatively low-cost step motor control ICs and off-the-shelf integrated drives.
Beyond waveforms, there is a world of variation in how the current that flows through each coil phase of the step motor is managed. Why do step motors even need a current controller?
The answer is inductance and back-EMF. However, it may not be possible to change operating parameters enough to improve performance without jeopardizing the overall design. In such situations, it might be best to go with a damper. Dampers are used to reduce resonances, reduce noise, and improve the response time of step motor systems.
They are mounted between the motor and machine, and work by energy-absorbing rubber absorbs shock to reduce shock impulses and dissipating the kinetic energy in resonances. This can greatly improve system stability, eliminate noise, allow for much smoother motion at low speed, and provide greater torque utilization at higher speeds. When performing fast point-to-point moves, a damper can enhance the system transient response and reduce settling time.
This improves control accuracy. Other stepper motor drivers like the LV can also handle microsteps, but they require the printer control board to send an individual step signal for each of those steps - which may limit speed because of the additional load on the board's MCU. The coils in the stepper act like speakers.
Its not that the stepper is making less noise, it's just making it in frequencies that are above the average person's hearing. To make a stepper perform a step, block signals are send to energize the coils to position the rotor. Such a block signal causes abrupt motion and triggers harmonic frequencies. This is audible as stepper noise. If the block signal is smoothed, the motion is more fluent and less noise will be observed.
A similar effect is achieved using micro-stepping. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Stepper motors can run very quietly. They need not make any more noise when attached to the scope as when held in your hand. It's common star party etiquette to run a quiet operation, and you will make a good impression of your system.
The noise of the switching stepper motor windings is greatly amplified when attached to metal and wood mounts. The mount acts as a drum. To run them quietly, isolate the stepper from wood and other resonant materials by a thin piece of rubber or styrofoam or something similar such as a mouse pad neoprene.
Use nylon screws or nylon bolts to attach the stepper to its mounting plate, further isolating the screws with rubber grommets. Use a short piece of automobile vacuum hose to attach the stepper to the input drive shaft of the gear reducer, leaving a gap of a millimeter between the shafts.
0コメント