The FAULHABER Group offers a complete line of programmable motion controllers with various communication and performance features to fit your application. We offer controllers with multiple interfaces like RS-485, DeviceNet, or RS-232, CANopen interface.
All controllers come complete with integrated servo amplifiers and on board memory for stand alone or macro execution.
FAULHABER also offers the BLD series PWM servoamplifiers are designed for 2 to 4 quadrant speed control of FAULHABER three phase brushless DC-Servomotors. For control of FAULHABER brush type coreless DC micromotors and motor tachometer combinations FAULHABER recommends the LC302, 4-quandrant, linear controller.
PRECIstep Stepper Drivers come in three versions, low and medium voltage and a current mode (chopper) drive, encompassing the full range of PRECIstep miniature DC stepper motors. Each series is available in three versions, from a simple full- and half-step drive to a complete driver with variable clock frequency and the ability to create specific motion profiles. Here are some notes on the application of our motion controllers and some answers to some frequently asked questions.
Electromagnetic - (EMI) and Radio Frequency (RFI) Interference in Motion Control Systems
The Importance of the Transceiver in Eliminating EMI/RFI in a Closed Loop Motion Control System
It's been a popular trend among OEM design engineers in the last decade to design autonomous motion control systems with the control electronics and motor in one compact package. However, for a few motion control applications there are sound reasons to buck this trend. The most popular reason - when motor real estate is tight and it makes more sense to put the control electronics farther away from the motor. Another reason might be that the control electronics can produce undesirable effects - like in hazardous work areas (for instance nuclear or gaseous environments). In a closed loop motion control system, distancing the motor from its drive electronics poses two major problems. First, over long distances, attenuation of the encoder feedback signals occurs due to the DC resistance of wire and normal line losses. In a closed loop system, this degradation of the encoder feedback is intolerable. Second, the wiring may absorb EMI/RFI noise produced by nearby electrical equipment further degrading the feedback signals.
There are a number of solutions that help circumvent these problems. Typically, these solutions involve converting the encoder feedback signals to a more robust type of signal.
One very expensive solution is a fiber optic driver. This device converts the electrical signals from the encoder and converts them to pulses of light transmitted over fiber optic cable. A fiber optic receiver can then be used to convert the light pulses back to the original electrical signals. Since light is not affected by EMI/RFI and fiber optics allows us to transmit light easily over very long distances, it can be an effective but expensive solution.
One inexpensive solution is a balanced differential driver, also known as a line transceiver.
Like the fiber optic driver, the line transceiver (capable of transmitting and receiving) also converts the encoder's electrical signals into a more robust type of signal.
In this case, the transceiver produces a "balanced differential" signal (typically 2-6 volts) which appears across a pair of signal lines. Each encoder channel signal is converted into a pair of signals (called differential signals). These differential signals can then be transmitted very long distances (up to 4000 ft). Another transceiver can sense the voltage state of the two signal lines and by examining the "differential" voltage across the pair of signal wires it can output a corresponding data logic state (zero or one). The differential voltage across the pair of signal wires is usually + 200mv and -200mv and represents a particular logic state.
Because the transceiver is looking for the differential voltage across an input pair (in essence, acting as a differential amplifier), it has two unique abilities. First, it has the ability to reject EMI/RFI common-mode noise and secondly, it can discern logic levels despite attenuation of the signal pairs. Therefore, the use of a line transceiver provides a way to distance your control electronics from the motor and provides a defense against EMI/RFI interference.
There are practical limits in distancing the motor from its drive electronics. For practical purposes a typical DC brush motor can be distanced 100-200 feet, more than adequate for most applications. However, there are techniques that can enhance that distance to 1000 feet if needed for special applications.
To determine when and how to distance your motor from your control electronics, or to determine the right number of transceivers in your next application, and when to use a closed or open loop motion control system, make sure you check with your motion control supplier. They should be able to supply you with an inexpensive and readily available off-the-shelf product or custom solution and plenty of sage advice.
By: Carlos Castellanos
Applications Engineer, MICROMO
New Miniature Motion Controllers Reduce Size While Increasing Functionality
In position and velocity servo control applications there are many factors that need to be considered during the design phase. If a motor-encoder combination needs to be positioned a long distance from the controller, the possibility of electro-magnetic interference affecting position accuracy is often overlooked. If space permits, placing the motor and controller in close proximity to one another is the simplest solution. New miniaturized motion controllers supporting serial communications provide the end-user with such an opportunity. Moreover, they have become-lightweight, compact, and powerful. Keep in mind that our perspective reflects decades of research and development into our product, the miniature motion controller and within our market, the miniature DC motor market.
Some of the new miniature motion controllers on the market combine both servo amplifier and controller into a single package. Supply voltages can range from 12-28 Volts and can output 5 Amps continuously with a peak current of 10 Amps and is suitable for brushless motors ranging in output from 10 Watts to 100 Watts. Its small size which can be, depending on the manufacturer, 2.5" x 2.25" x 1.1" high, allows it to be installed in areas with minimal space availability and in close proximity to the motor. In addition, when the controller is connected to a host PC, it can operate in a slave mode using RS-232 serial communications.
How do these new controllers reduce package size and total system cost? One reason is that they eliminate the encoder. Certain controllers are available with brushless motors containing linear Hall effect sensors, which allow for positioning resolution within 1/1000th of a revolution and negate the need for an additional encoder. The linear Hall effects reside inside the motor in place of standard Hall effects and are used as position and commutation feedback. Keep in mind that small package size does not mean limited system versatility; some controllers contain a powerful 16-bit microprocessor. Some controllers can function in various control modes-position and velocity control mode, torque control mode (through current limiting), and stepper motor mode that allows you to program the number of steps per revolution and step width. Ramping, triangular, trapezoidal, and more complex motion profiles are also available from some manufacturers as well as speed command input. This input is generally available in either analog or digital form with an open collector fault output on the board, which can be used as a homing input or a direction of rotation input.
The new miniature motion controllers (depending on the manufacturer) are generally easy to program with a highly functional ASCII command set. You can communicate with the controller via a PC using a terminal emulation program such as HyperTerminal or demonstration programs supplied by the controller vendor. The ASCII command set consists of four parts: a node address, a command word, a number (usually a value associated with a command word), and a carriage return. The advantages are that it is simple for the end user to program, it does not require additional software, and is usable with any computer system that supports RS-232 serial I/O.
Why use the RS 232 serial interface? In communicating between the miniature motion controller and its host over very long cable distances, using an RS-232 serial interface is extremely reliable. There are many applications where the motor-encoder combination is a significant distance from the controller. Usually a line driver transmitter is used on the encoder side and a line receiver on the controller side in order to transmit and receive the encoder signal reliably. Shielding motor phase wires and twisting or separately shielding motor Hall sensor wires is also necessary to reduce the effects on the system from the surrounding environment. That recurring advantage-the low-profile design of the miniature motion controller allows it to be placed close to the motor-so that any significant distance is taken up by the RS-232 cable interface between the host and the controller. Again, depending on the manufacturer, in addition to serial communications mode, it can also be used in a stand-alone mode. Some have an EEPROM (electrically erasable programmable read-only memory), which stores the motion control program so that the controller can be used without connection to a host, allowing the system program to be actuated by the external event inputs on the controller.
Virtually any market that requires precise position and velocity control and long motor life is a potential market for this type product. This new controller might be very effectively used in various applications in the medical market. For example, it could be used in-laboratory instrumentation requiring a bench top or stand-alone blood analyzer, automated drug-dispensing equipment, or machines used to analyze DNA. Moreover, one increasingly prominent application for this motor/controller package is robotic surgery.
Finally, a good motion control supplier can help configure the right controller to fit your application. They can adjust the controller's proportional and integral gain to suit your requirements or they can assist with the programming and debugging of the motion control sequences. Take advantage of their specialized knowledge. The advantages to the end-user are less frustration and reduced product development time.
MicroMo offers a broad range of controllers and amplifiers to fit most any application complete with the features discussed in this note. Contact our applications engineering department for more information on our MCDC, MCBL and MVP lines of controllers.