11/25/2020 at 15:46 •
The PA-12 electric linear actuator is a fantastic example of lean design principles and represents the future of linear motion. If you are looking for a device that can deliver best-in-class performance in a compact package, look no further. The PA-12 is packed with modern solutions to recurring problems, and this article will provide a look into the main features of this actuator’s design. This linear actuator is purpose-built to provide the most precise movement possible at a high resolution, without requiring the user to determine control parameters or to compensate position readings for different load conditions. To do this, the actuator has a very high precision potentiometer with a built-in filter to reduce the electrical noise, and a very light motor to reduce the impact of inertia. We also sell PA-12 actuators with coreless motors, which can provide a significantly better performance than cored motors, and further contributes to increased accuracy.
This electric actuator come equipped with an on-board computer that will handle all the necessary calculations. It just requires the user to supply the commands in either TTL or RS-485 format. Alternatively, PA-12 can be connected to LC-12 computer controller, and you will be able to send commands through an interface on your PC. With all of that in mind, lets dive into the PA-12 and all it has to offer!
We had an independent test performed on our PA-12 actuators to calculate its movement precision. The test was to accurately execute two servo counts per movement command, which would amount to 0.001074” per move. Measurements were gathered using a precision laser position indicator and the actuator also had a 15 lbs load attached to it for both extension and retraction. The results can be seen in the graphs below.
Most common instruments cannot accurately perceive a change in position that small. If the actuator were moving in larger increments, the results would have been even more precise. This movement is based on two factors – high precision from the built-in potentiometer and a properly calibrated PID controller. The parameters for PID control can optionally be changed through the digital commands but it is not recommended.
Cored vs Coreless Motor
PA-12 can come equipped with either a cored or a coreless DC motor. We will take you through the advantages and disadvantages of both.
In a typical DC motor, a coil is wound around the iron core of the rotor. When a current is applied to the coil, it creates a magnetic field that, together with a stator, causes the rotation of the motor. The iron core brushed DC motor is a tested, reliable, low cost option. A cored, brushed DC motor would be able to run from straight-line DC voltage and handle high torque because of the iron core keeping everything rigid. The core also helps the motor achieve higher current draws because it acts as a heat sink and allows the heat to dissipate. This type of motor is very simple and yet effective, but it does have a few disadvantages.
A cored brushed DC motor tends to have lower acceleration and deceleration due to the added weight from the iron core. This motor also tends to have higher inductance, which means that there are more accidental electrical arcs between the commutator and the brushes. This effect would increase the wear on the brushes over time.
A coreless brushed DC motor is the solution to many of these problems. A coreless motor is constructed using a self-supporting winding mesh that does not need the core to keep it in the right shape. This makes the rotor very light, which means it can accelerate and stop much faster. It is more efficient, requiring less current to accomplish the same torque as the iron core motor. These types of sophisticated windings also have lower inductance, which means that the arcing between commutator and the brushes happens at a lower power and reduced frequency....Read more »