Non-captive types of lead screw driven linear motor actuators are different from the more common external versions in that they allow the lead screw to completely pass through the motor. This fundamental difference offers advantages for those that have limited space available or are looking to shrink the overall size of their design package.

With an external actuator, the object being moved is mounted to the nut, and the screw rotates providing the motion along the length of the screw.

By contrast, in a non-captive actuator, the payload or object being moved is attached to the motor, and has screw ends that are typically fixed. In most cases, this setup can allow for a shorter overall screw to be used. It is also ideal for adding the external linear guide bearings that are almost always required for non-captive applications. They provide stiffness and eliminate deflection that causes premature wear on the nut, screw, and internal motor bearings.

A less common situation is where the device or payload is attached to the end of the screw. This is only used for very light loads and requires external linear guidance for stiffness. It is an arrangement that also requires clearance for the screw to extend out the opposite side of the motor.

One feature common to all non-captives is that the nut driving the screw is internal to the motor. Traditionally, this nut has been a standard nut with no mechanism to account for the play between the external threads of the screw and the internal threads of the nut. If, in this scenario, an anti-backlash capability was needed, manufacturers might be able to provide a custom solution, but with significantly higher cost and extended lead times.

To avoid this problem, PBC Linear offers the choice of a standard nut or anti-backlash nut within their non-captive linear actuators. We have the only anti-backlash nut and lead screw assembly available off-the-shelf in a non-captive configuration. This unique combination offers the best positional performance available in a non-captive hybrid actuator by utilizing our patented Constant Force Technology (CFT), which provides greater than two-times the superior backlash compensation as tested against competitors.

This advantage means that the self-lubricating nut will provide lubricant-free, consistent performance and preload over its lifetime. In addition, screws are available either uncoated or with a proprietary PTFE coating. These screws come with standard lead accuracy of 0.003 inches per foot, which is three-times better than typical screws on the market.

Non-captive linear actuators from PBC Linear go beyond the simple definition of motor and lead screw. They excel because they have been designed from the inside out, providing superior performance in linear motion applications.

With an external actuator, the object being moved is mounted to the nut, and the screw rotates providing the motion along the length of the screw.

By contrast, in a non-captive actuator, the payload or object being moved is attached to the motor, and has screw ends that are typically fixed. In most cases, this setup can allow for a shorter overall screw to be used. It is also ideal for adding the external linear guide bearings that are almost always required for non-captive applications. They provide stiffness and eliminate deflection that causes premature wear on the nut, screw, and internal motor bearings.

A less common situation is where the device or payload is attached to the end of the screw. This is only used for very light loads and requires external linear guidance for stiffness. It is an arrangement that also requires clearance for the screw to extend out the opposite side of the motor.

One feature common to all non-captives is that the nut driving the screw is internal to the motor. Traditionally, this nut has been a standard nut with no mechanism to account for the play between the external threads of the screw and the internal threads of the nut. If, in this scenario, an anti-backlash capability was needed, manufacturers might be able to provide a custom solution, but with significantly higher cost and extended lead times.

To avoid this problem, PBC Linear offers the choice of a standard nut or anti-backlash nut within their non-captive linear actuators. We have the only anti-backlash nut and lead screw assembly available off-the-shelf in a non-captive configuration. This unique combination offers the best positional performance available in a non-captive hybrid actuator by utilizing our patented Constant Force Technology (CFT), which provides greater than two-times the superior backlash compensation as tested against competitors.
This advantage means that the self-lubricating nut will provide lubricant-free, consistent performance and preload over its lifetime. In addition, screws are available either uncoated or with a proprietary PTFE coating. These screws come with standard lead accuracy of 0.003 inches per foot, which is three-times better than typical screws on the market.

Non-captive linear actuators from PBC Linear go beyond the simple definition of motor and lead screw. They excel because they have been designed from the inside out, providing superior performance in linear motion applications.

https://zuobianyoubain.doodlekit.com/blog/entry/5834560/how-to-use-incremental-encoders-with-stepper-motors
http://www.christ282.de.rs/blog/post/how-to-avoid-resonance-issues-in-stepper-motors-35837

Linear Stepper actuator motors are typically controlled by a driver and controller. The amount, speed, and direction of rotation of stepper actuator motors are determined by the configuration of digital control devices. The main types of control devices for stepper actuator motors are: stepper actuator motors control links and stepper actuator controllers.

Linear Actuators – Category Shot
Type of Stepper Actuators

There are three basic types of stepper actuators. The stepper actuator motor types vary by their construction and in how they function. Each type of stepper actuator offers a solution to an application, in different ways. The three basic types of stepper actuators include the Variable Reluctance, Permanent Magnet and Hybrid Actuators.

Variable Reluctance (VR) Stepper Actuators

VR stepper actuators are known for having soft iron multiple rotors and a wound stator. The VR stepper actuators generally operate in step angles from 5 to 15 degrees, at relatively high step rates. They also possess no detent torque. In Figure 5, when phase A is energized, four rotor teeth line up with the four stator teeth of phase A by magnetic attraction. The next step is taken when A is turned off and phase B is energized, rotating the rotor clockwise 15 degrees; Continuing the sequence, C is turned on next and then A again. Counterclockwise rotation is achieved when the phase order is reversed.

Permanent Magnet (PM) Stepper Actuators

Linear Actuators – Type – PM Non-CaptivePermanent Magnet Stepper Actuators differ from variable reluctance stepper actuators by having permanent magnet rotors with no teeth. These rotors are magnetized perpendicular to the axis. When the four phases are energized in sequence, the rotor rotates as it is attracted to the magnetic poles.

Linear Actuators – Type – Hybrid Non-Captive
Hybrid Stepper Actuators

Hybrid Stepper Motor Actuators combine qualities from the both permanent magnet and variable reluctance stepper actuator motors. The Hybrid stepper actuator motors have some of the desirable features of each. These stepper actuator motors have a high detent torque, excellent holding and dynamic torque, and they can operate in high step speeds. Step angles of 0.9 to 5.0 degrees are normally seen in hybrid stepper actuator motors. Bipolar windings are generally supplied to these stepper actuator motors, so a single power supply can be used to power the stepper actuator motors.

http://www.dsprobotics.com/support/viewtopic.php?f=5&t=35982
https://openrcforums.com/forum/viewtopic.php?f=27&t=12394&sid=c38d0ca9c9a33272b1d3109843a038cf

Recently almost every medical device I design requires a stepper motor. After working with these motors so frequently, I’d like to share what I’ve learned about medical device stepper motors, the different types of stepper motor configurations, and how to drive stepper motors properly.

Stepper Motor Drive Configurations
Stepper motors typically come in two motor winding configurations. Before selecting which configuration is appropriate for your application, you should understand the basic difference between the two. This choice will be important when selecting how to drive the motor.

Pro Tip: You can use a unipolar motor as a bipolar motor if you ignore the center tap. This can come in handy if a particular design of motor is only available in a unipolar configuration.

Stepper Motor Drive Signals

Typically three types of drive signals are used to control the motion of a stepper motor. Each drive type increases in complexity, but adds additional features and options.

A wave drive only energizes one phase at a time. Wave drives are simple to implement with basic hardware, but are rarely used. Because only one coil is energized at a time, torque is significantly reduced.

Stepper Motor Drive Circuits
The most common methods for driving a stepper motor include a simple constant voltage or L/R (L refers to electrical inductance and R stands for electrical resistance) driver, a chopper drive, or a sine wave/micro-stepper driver.

Stepper Motor Integrated Drivers
Once a stepper motor hybrid has been selected to suit its mechanical requirements, the next thing is to get that motor turning. It is easier than ever to make a motor operational by selecting an off the shelf stepper motor driver IC or development board. Many of these boards provide features such as current feedback, built in acceleration profiles, and even onboard path planning for more complicated motion control.

Something About Holding Brakes for NEMA23 Stepping Motors

Choice For A Pancake Stepper Motor With Absolute Encoder

The motor and motor control markets are thriving in a number of areas, particularly medical and robotic applications. Also, there is a rich demand for small, efficient, high- and low-torque, and high- and low-power motors in the automotive sector.

Brush DC Motors
Around since the late 1800s, dc brush motors are one of the simplest types of motors. Sans the dc supply or battery required for operation, a typical brush dc motor consists of an armature (a.k.a., rotor), a commutator, brushes, an axle, and a field magnet (Fig. 1) (see “Brushed DC Motor Fundamentals”).

Brushless DC Motors
In terms of differences, the name is a dead giveaway. BLDC motors lack brushes. But their design differences are bit more sophisticated (see “Brushless DC (BLDC) Motor Fundamentals”). A BLDC motor mounts its permanent magnets, usually four or more, around the perimeter of the rotor in a cross pattern (Fig. 3).

To Brush
When it comes to a loosely defined range of basic applications, one could use either a brush or brushless motor. And like any comparable and competing technologies, brush and brushless motors have their pros and cons。

Or Not To Brush
BLDC motors have a number of advantages over their brush brothers. For one, they’re more accurate in positioning apps, relying on Hall effect position sensors for commutation. They also require less and sometimes no maintenance due to the lack of brushes.

The Choice Lies In Our Apps
The bottom lines for making a choice between components of any type are the type of application and the cost cutoff for the end product. For instance, a toy robot targeting the six- to eight-year-old market may require four to nine motors. They can all be brush or brushless dc components or a mixture of both.

The automotive industry also puts higher-power BLDC motors to work in electric and hybrid vehicles. These motors are essentially ac synchronous motors with permanent magnet rotors. Other unique uses include electric bicycles where motors fit in the wheels or hubcaps, industrial positioning and actuation, assembly robots, and linear actuators for valve control.

What makes brushless vibration motors long life? The clue’s in the title!

The precious metal brushes are typically the most common source of failure that limits the lifetime of normal DC motors. They are integral to the operation of our eccentric rotating mass vibration motors in the ‘Vibration Motor’ section of our Product Catalogue.

Whilst our recent Application Bulletin demonstrated our miniature vibrating motors are achieving an MTTF in the region of 1,500 – 2,000 hours some applications demand even longer performance.

So to improve life the solution seems simple, find a replacement for the brushes! This is actually quite complicated, the job of the brushes was to reverse the direction of the current through the internal metal windings (this ensures a constant direction of rotation of the shaft).

This is achieved by sensing the position of the internal windings and electrically changing the direction of the current at exactly the right time. To do this, we use the Hall Effect to calculate the position of the motor and change the drive signal accordingly. For more information on this, see Application Bulletin 018: Driving Brushless Vibration Motors.

Instead, with this blog post, we wanted to share an interesting infographic found on spingarage.com. Those interested in seeing exactly how the drive signal changes with the output from the Hall Effect sensors can study the image below.

Thankfully if you find the graphics confusing, you don’t really need to fully understand it. Our 910-101 has an integrated driver chip that handles the communication automatically, and we have a suggested circuit for the 912-101 that you can easily implement.

Of course, if you have any questions about brushless dc motors or how to drive them, please get in touch with us!