Frequently Asked Questions
A typical servo motion control system includes the following components: PLC/Motion Controller as the brains, HMI for User Interface, Servo Drives, Servo Motors, and other 10 devices (sensors, actuators). Servo drives and motors are sized based on the power requirements of the application. Sensors, HMI, and PLC/Motion Controller are logic components whose size does not change with the application power.
The only difference between stepper motor and servo motor based motion control system is the motor and drive: in the case of stepper based system the stepper drive and stepper motor replaces the servo drive and servo motor. Generally speaking, servo motor/drive technology has superior performance than stepper motor/drive technology. However, by the advancements in digital current commutation technology and its applications in stepper drives, the performance of Stepper motor/drive technology is increasily competitive with that of servos. In addition, stepper motor/drive systems are generally lower cost than servo motor/drive systems. Further, stepper system are limited to fractional or a few horse power applications, where as servos can be tens or even hundreds of horse power.
Every servo motion control axis has a closed loop control algorithm called “servo algorithm”. This algorithm logic mostly has what is called PID (“proportional-integral derivative” terms) logic that acts on the servo error and generates the command signal. Every manufacturer implements their own proprietary servo (PID) algorithm logic. End user can adjust (“tune”) the parameters called “gains” of the algorithm. Although the textbook example of PIDs have only three parameters, state of art servo control algorithms have over 300 parameters to adjust. However, not all of them need to be tuned for every application. In EtherCAT based motion control systems, the servo algorithm is almost always implemented at the servo drive, hence tuned there.
Every motion transmission mechanism (gears, ball-screws, belt and pulleys) have some backlash and it can get larger over time and under load. If the backlash is in the order of the desired positioning accuracy of the servo system, the best solution is to use dual position feedback: one encoder integrated to the servo motor, second encoder connected to the load/tool (i.e. linear encoder connected to the moving stage of a ball-screw). Then we can measure the actual backlash and compensate for it in the servo control algorithm. However, the dynamic (transient) motion control quality of the backlash compensation may not be as smooth or easily controlled. Therefore, careful system component selection (i.e. resolution of encoders) as well as servo control algorithm (logic) intelligence are key factors in successful compensation of backlash in high precision positioning servo systems using dual feedback.
Friction exists in nature between any two surfaces that moves relative to each other. In our cars, it is the friction that allows the tires to provide traction and move the car. In that case friction is a good thing and without it, the car would not move, i.e. on ice. However, friction in servo motion control systems, especially stiction (Coulomb) friction, is undesirable. It results in positioning error. If the stiction friction is too large, the position control accuracy of the servo system is adversely affected. The servo positioning axis would “hunt” (oscillate with stuck-move-stuck-move) type small motion around the desired position. The best way to deal with friction is to have a mechanical system designed and maintained such that the friction in minimized and the resulting error in positioning is acceptable. Active control techniques are based on high resolution position measurement, low noise servo drive and intelligent servo control algorithms that has friction compensation logic.
Every mechanical system that has inertia and stiffness (finite rigidity) has resonance freqeuncies. The resonance frequency (or frequencies) are determined by the structural material distribution of the mechanical system. In simplest form, a mass (m [kg]) connected to a spring (k [Nt/m]); has resonance frequency square root of k divided by m. For a given mass, the higher the stiffness of the system is, the higher the resonant frequency is. If there is zero damping in the system, if the system has input signal that has sinusoidal content and if the sinusoidal content is at the resonant frequency, the response would be so large that the system would vibrate wildy to self-destruction. The level of wild vibrations are significantly reduced if there is sufficient damping in the system which can be introduced by mechanical design and active control methods. In servo systems, the common way of dealing with resonance problems is to implement Notch filters in the servo control algorithm. Notch filters would work well if we know the resonance frequency (or freqeuncies) accurately. If they are not known accurately (i.e. due to change in the net inertia during operation, the resonant frequencies may change), then Notch filters would not work well.
In some applications, such as press, injection molding, screw-in, assembly, a servo axis needs to be both position and force controlled. In some part of the motion cycle, we need to control position. At some condition, we need to switch to force control mode. Then on another condition, switch back to position control mode. This kind of system requires a secondary force (pressure or load) sensor in addition to the servo motor position. The servo control algorithm implements the conditions when and how to smoothly make the switch between two closed loop servo control modes.
AMAX-5580 Controller requires 24 VDC power input. The amount of current it may need depends on the number of I/O modules connected to it on the left and right side. Generally 60W power supply is sufficient. If you already have your own 24 DC Power Supply, that can provide this much power, you don’t need to buy a DC power supply.
There are three different ways EtherCAT I/O modules can be connected to the AMAX-5580 controller:
- Directly attached to the right side of the backplane.
- Connect to the EtherCAT channel in the Servo Drive channel. EtherCAT I/O pack requires EtherCAT Coupler Module.
- Connect it to a second EtherCAT channel (not with the Servo Drive ‘s channel) via EtherCAT Extension Module connected to the AMAX-5580 base unit and EtherCAT Coupler Module on the I/O pack.
The variants of CODESYS are as follows:
- Control RTE: Real time software PLC programmable with IEC 61131-3 Development System CODESYS.
- Softmotion: CODESYS Softmotion tool kit to implement the motion functionality (single and multi axis control)
- Softmotion CNC: Provides 3D – CNC (G – Code) for motion control, including interpolator and kinematic transformations.
The Windows 10 IoT Core device will boot to the default app instead of a desktop-like PC. The purpose of this application is not only to provide you with a friendly shell to interact with upon first boot, but to also allow you to use the open-sourced code for this application so that you can use these features to plug and play your own custom application(s).
Not all folders on your device are accessible by Universal Windows Apps. On Windows 10 IoT Core you can use the FolderPermissions tool to make a folder accessible to a UWP app
Devices which are compatible with have an ESI or EDS file from the manufacturer and which are compatible with EtherCAT, can be connected to the AMAX 5580 controller. The ESI or EDS file must be installed in the CODESYS repository.
The Servotech Vision library provides the requisite base code for the custom Servotech transmission protocol built on the TCP/IP stack. The data vision data is computed real time and packaged into a special data structure that is accessed by the transmission library. On the controller end, the data is unpacked and made usable by special function blocks, designed to be integrated into any other logic for coordinated motion.
The lens resolution indicates the total number of image points that can be created by the lens for the camera sensor. Typically, the lens selection is made based on the camera resolution, with the camera itself being the limiting factor. Ideally, the camera resolution should not exceed the lens resolution. While it is permissible for the lens resolution to be much higher for any given application, considerations should be made as to the cost of an unnecessarily high lens resolution.
Currently, we only support GigE cameras. While the Processor itself has USB ports, they are not designed for camera usage as they are not connected to any capture card or frame grabbing hardware. The processor itself has no spare PCI for USB expansion for cameras.