Headquarters: SIKO GmbH Weihermattenweg 2 79256 Buchenbach Germany Phone+49 7661 394-0

Motor feedback systems: precise position feedback

Electrical drive units in industrial automation processes require precise and reliable control. Sophisticated sensor systems such as those supplied by SIKO are essential with direct drive systems in which the motor and machine are directly connected and no gear unit is required. A motor feedback system signals the position and speed measurements of the motor to a subsequent electronic system. This in turn controls at which speed, in which direction and with which degree of precision the motor should run. The measurement system must be fully aligned with the demands of the application to enable the electrical drive to work as efficiently and reliably as possible while conserving resources. The SIKO magnetic motor feedback systems satisfy the high demands of industrial drive technology regarding precision, resilience to external influences, shock and vibration as well as having an extremely compact design.

Incremental and absolute position feedback

When selecting a motor feedback system it should also be considered whether a – less expensive – incremental or an absolute solution is required. The absolute position feedback is more convenient than the incremental option, as the sensor always knows exactly at which position it is due to the unique absolute coding – also in a non-energized condition. In contrast, incremental coding with regularly arranged north and south poles always requires referencing to bring the sensor back to a reference point. In some applications, especially those that are critical for safety, absolute motor feedback solutions are therefore essential.

Motor feedback for linear direct drives and rotary direct drives

When selecting the correct measuring equipment for the motor feedback, a difference is made between linear and rotary direct drives in various sizes and versions. SIKO solutions are available for the following linear and rotary requirements:

Linear motor: iron-core or ironless

Linear motors are used where a very good force/mass ration, optimum synchronization and constant speed as well as the highest path accuracy is required.
All versions require exact position feedback as available in the SIKO MagLine series. Both incremental and absolute position feedback is possible. Small, compact designs permit simple integration and efficient commissioning. The SIKO magnetic measurement systems have an outstanding positioning accuracy and control quality in dynamic processes. The advantages with motor feedback for linear motors at a glance:

  • Completely non-contacting and wear-free

  • Robust when exposed to shocks and vibration

  • Simple installation and commissioning

  • Incremental and absolute measuring technology


Torque motor: Position feedback for rotary motion

On rotary direct drives the torque drives are becoming increasingly widespread and important. Rotary direct drives work in a similar way to the linear drives. However, on rotary motors the coil is turned in a magnetic circuit. Torque motors generally have an end-to-end hollow shaft to permit routing of cables or compressed air lines. Torque motors are best suited for applications requiring high torque combined with ideal synchronization. With the high drive torque, fast acceleration is possible that lends the system a high degree of dynamics. The demands on the sensor system are correspondingly high. The SIKO advantages at a glance:

  • Small sensor designs that can be integrated

  • Scale (magnetic ring) for different sizes that can be integrated

  • Interfaces with real-time signal output

  • High accuracy for exact positioning feedback and optimum control quality

  • Incremental and absolute measuring technology


Gantry axes: Motor feedback for two linear drives in one portal

Gantry axes (portal axes) are special linear drive types. These are two separate linear motors that run in parallel on two rails and that are controlled together in the control unit. Gantry axes are very strong and accurate and are often used, for example, in handling, mounting or pick & place lines. One axis is used to move over a workpiece, while the other axis lowers a tool for machining. The low space requirements are advantageous, as the gantry axis moves exactly where it is required for machining. Another method would be to position the workpiece on a table and to move the table to and fro for machining. This requires, however, much more space. With portal axes, precise interaction of both rails is important, and this is only possible with cleverly designed measuring equipment for determining the position and speed. Both feed motors must each be synchronized with its own measurement system. In addition, positions on the X and Z axes must be measured. The advantages of SIKO measuring equipment:

  • Insensitive to soiling and moisture

  • Simple installation

  • High positioning accuracy


Motor feedback under extreme conditions

Motors often work under very rugged conditions, which not only make great demands on the motor itself, but also on the measuring sensors. The motor feedback system also has to be able to display exact positions and speeds in dusty conditions (stone processing), moisture (glass cutting), in an oil bath or under mechanical stress such as shock or vibration. The SIKO magnetic speed and angle measurement system are predestined for these extreme demands; the advantages for example for oil-immersed applications:

  • Long service life (non-contacting and bearing-free)

  • High operational safety

  • Protection rating up to IP69K

  • Flexible, customized solutions


Robotics: Compact sensor systems tailored to customer requirements

Torque motors are used in robot applications such as pick-and-place modules. The robot arms are normally encapsulated and contain small to medium torque motors. The measurement tasks are detection of rotary and swiveling movements. The challenge is the small available space. Sensors for motor feedback must be very small and if possible they should be non-encapsulated when installed. SIKO always looks for customized solutions for each application, depending on the space available. Normally the electronics are used without a housing. The advantages at a glance:

  • Very compact design for integration in torque motors

  • Customized solutions, for example with open PCB

  • Adaptation of the scales to the existing space

Magnetic motor feedback solutions from SIKO: MagLine

Magnetic motor feedback systems have proven their worth in a number of applications and sectors in which the measuring sensor system has to be robust, non-wearing, durable and highly accurate such as linear and rotary guiding and drive technology, wood, metal, stone glass and plastic machining, warehouse and conveying technology, elevator technology or in demanding conditions such as in an oil bath or on balancing machines. SIKO MagLine works in accordance with the principle of non-contacting scanning of magnetic fields and converts its measuring values to digital or analog signals. Depending on the requirements, four product families offer coordinated solutions made up of magnetic sensor, scale (magnetic strip or magnetic ring) and downstream electronic systems: MagLine Micro, MagLine Basic, MagLine Macro and MagLine Roto. With SIKO MagLine you profit from the following features:

  • Completely non-wearing

  • Insensitive to external influences such as dust, moisture, oil and grease etc.

  • Extremely robust when exposed to shocks and vibration

  • High system and repeat accuracy

  • Magnetic strips that are encoded by SIKO in specially developed processes

  • Incremental and absolute encoding possible

  • Simple handling and installation (magnetic strips on rolls for cutting to length)

  • Durable and economical


More safety: Magnetic sensor with SIL2 certificate and DRIVE-CLiQ interface

The compliance with functional safety standards is becoming increasingly important in the mechanical engineering sector. It is therefore advantageous if individual components already have safety certification, and it is no longer necessary for them to be included in the safety concept of the overall system. The MagLine-Sensor MSA111C is the first absolute measurement magnetic sensor with an open design – in which the scale and the electronics are mechanically fully decoupled – that is certified to SIL2. It was developed on the basis of the Siemens DRIVE-CLiQ interface, the SIL capability of which enables it to implement safety functions. Specific applications require a safe position or a reliably lowered motor speed to protect the operator. It must therefore be ensured that the motor feedback system always reliably communicates the signal – with the MSA111C the user has certified certainty.


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You can find additional information in our flyer "Motor feedback systems"
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Read our white paper "High productivity with open motor feedback systems"

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