Motion Control & Drives

A coherant, Modular and forward thinking design platform

April 2000 Motion Control & Drives

Bosch Servodyn-D designed for the present while allowing for future developments. All aspects of the processor cards and power stage circuitry employ digital techniques which means that the concept, from supply modules to drive modules, is well suited for synchronous and asynchronous motors.

Two choices of module

One with a simple hardware arrangement for everyday requirements, the other for higher specification tasks and incorporating a modular backplane. These two versions of Bosch Servodyn-D can be combined to suit any eventuality and all this fits into a control cabinet with a depth of 300 mm.

Optimised processing power

Depending on the selection of the drive system command values, Bosch use two different processor cards each having been designed to provide the optimum performance in their class:

* A SERCOS interface gives performance and functionality. Offering the advantage of realtime execution and noise free transmission by optical fibres as well as the option to combine control and drives from different manufacturers. Digital position, speed and current control is handled by a 32-bit signal processor.

* In the most common applications of drive control an analog voltage is the popular choice for selling the command value. Here a VeCon chip is used for digital speed and current control. It is also possible, as an option, to use the VeCon chip for implementing motion control.

Motion control

The drive concept can be used to integrate motion control into the actual servo motor amplifier. This produces a cost-effective solution to, for example, many simple handling tasks since a higher ranking position controller is no longer required.

Exact positioning-with repeatability

Up to 32 independent motion command blocks can be stored in the Servodyn-D module. Each block contains information defining the target position of the movement along with acceleration and velocity settings. This is programmed into the module using an RS232 interface and selected by standard 24 V I/O signals. A high accuracy of movement is guaranteed by the digital technology and short cycle times employed at all levels. This eliminates the possibility of analog drift through the effects of temperature change or ageing.

Programmable speed or angle synchronisation

Any number of Servodyn-D motion control slave modules can be linked to follow a master axis in synchronised speed (electronic gearbox) or angle (electronic cam) control. The master module may use either the internal encoder emulation or an external measuring system as its reference signal. If an external source is used, then a number of different options are available through the OM1, OM2 and OM3 "slot-in" cards. The digital operating system allows easily programmable factors with minimum synchronisation errors because of the ability to run at high gain and short cycle times.

Mechanical cam emulation

When used in the master/slave synchronisation mode, the Servodyn-D modules can be used to emulate the function of mechanical cam systems. The movement of the slave axis is stored in a lookup table which relates precise slave motion against the rotation of the master axis in the range from 0 to 360° as determined by the geometry of the cam. Multiple slave axes, each with its own programmed motion profile, can be coupled to a single master axis.

Electronic "nameplate"

To simplify integration of the servo module is to its connected motor, each IGBT power stage and each motor has an EEPROM containing that devices unique characteristics. On power up the drive module is able to recognise the connected combination and automatically set the correct operational parameters in its working memory.

Integrated machine safety

Axis movement and motor torque are monitored by an integral safety circuit which has dual channel redundancy. This is in combination with:

1. Modules with SERCOS interface.

2. In conjunction with regenerative power supplies and mains connection modules.

This safety concept has been developed in collaboration with an international standards group for machine safety. Servodyn-D is also compliant with all other relevant European directives.

Motion control for standard positioning operations

Bosch believes it has opened the way to inexpensive decentralised design concepts by integrating the control functions within the drive system. Servodyn-D's data-storage memory can accommodate up to 32 positioning command sets including end position, acceleration rate, deceleration and maximum velocity. This makes it possible to define precise point-to-point motion as well as absolute and incremental travel.

An array of options for feedback interrace

Graduated-response motor monitoring systems adapt measuring precision to fit the actual requirements.

Servodyn-D converters can employ various modules to interpret data from an extended range of sensory systems while a special option card allows analog output of travel measurements. In addition, converters with an analog interface also include integrated encoder stimulation as standard equipment.

Electronic data plate

The converter's IGBT amplifier circuit and the attached motor each contain an integrated EEPROM - used to store the required operating data. The drive-control microprocessor automatically adapts the closed-loop motion control’s opening parameters to reflect the system's combination of motor and module. Rapid identification of drive system components eases service and maintenance.

Reliability through redundance

The redundant safety concept provides a reliable back-up to monitor the drive system during set-up operations, without the need for a second direct monitoring system. The motion-control system achieves full compliance with EN 954-1 by incorporating all of the functions defined in Category 3, making additional monitoring devices unnecessary. Extensive security functions covering such areas as voltage, current, temperature, short-circuit and grounding protection are all incorporated. The resulting high level of system reliability ensures trouble-free operation with cable lengths of up to 100 m, even without additional electronic devices.


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