Motion Control & Drives


Important Development in servo technology

April 2000 Motion Control & Drives

'As well as being a performance enhancer now, SLM technology is also a gateway to the future. Its integration into PC-Based motion systems opens up a whole new vista for optimised multi-axis control in the Millenium."

'M'Ax with SLM (speed loop motor) technology is the most radical and the most important servo development in years," says Control Techniques' Bill Drury, Executive Vice-President, Technology. "The really exciting thing about the technology is that it has been developed for the mass market. This means that machine manufacturers in all industry sectors are able to benefit from unparalleled levels of axis performance at low cost. The SLM system effectively overcomes, in a highly cost-effective way, the problems traditionally experienced with conventional high-end servo technology which is nowadays approaching its limits due to the physical constraints imposed by high resolution position acquisition.

Figure 1.The revolutionary M'Ax with SLM technology
Figure 1.The revolutionary M'Ax with SLM technology

The SLM system uses a combination of Control Techniques' four-wire, ASIC DriveLink technology and motor-mounted SinCos encoders to achieve an application invariant 20-fold increase in position feedback resolution (over 8,3 million points per revolution). This is achieved by integrating speed and position control within the feedback system on-board the servo motor. As a result, the SLM is able to overcome the degradation in performance experienced with encoder feedback signals when synchronising multiple servo axes on machines as operating speeds increase. An additional benefit is that the SLM system performance is independent of the number of axes employed. The system cost can be optimised for the particular application.

Figure 2. Conventional servo wiring - total 30/32 connections
Figure 2. Conventional servo wiring - total 30/32 connections

The technological benefits provided by the SLM system also translate into reduced system costs. Installation time is cut and start-up time is optimised, as a result of using an intelligent encoder which uploads such data as encoder to motor shaft alignment, encoder disk mounting accuracy offset and the motor map to the drive, automatically, on power-up. In addition, component and maintenance costs are slashed as a result of reducing the total number of interconnections on a typical machine axis by 57% (from 28 to 12), when compared to a standard servo encoder solution. This is significant when it is considered that one of the major reasons for system failure today relates to interconnecting cables.

Figure 3. M'Ax servo wiring - total 12 connections
Figure 3. M'Ax servo wiring - total 12 connections

Control Techniques' development of SLM technology stems from the basic premise that the key to achieving significant performance enhancements with servo systems is to obtain high quality, undegraded position feedback. Sine/Cosine (SinCos) encoders help in this respect but the problem with these is that their signals have to be conditioned for transmission to drives and controllers. If there were no need to transmit this data then the conditioning issue could be avoided. One way in which this could be achieved is by locating the position loop and velocity control loop in or alongside the encoder. This thought process led to the development of SLM system. One of the essential demands of the system is that each of the system components must be capable of communicating with each of the others in a robust and reliable way and provide a data throughput rate sufficient for servo applications.

Figure 4.SinCos signals with interpolated position.
Figure 4.SinCos signals with interpolated position.

This important issue has been addressed by the development of a dedicated ASIC, which forms the heart of all communications between individual parts of the overall system.

By placing a dedicated ASIC in each of the system components (motion controller, unimotor SLM and the drive), all communications are taken care of by the hardware protocol controller within the ASIC, which also has built-in error detection, such that zero overhead is placed on any of the microcontrollers dedicated to the control algorithms. The ASIC implements synchronised fault-tolerant communication between the controller and the drive system components via a standard two-wire RS485 physical layer at a data rate of up to 2,5 Mbps. Typical cable lengths of up to 100 m can be reliably implemented. In addition, the ASIC enables users to optimise on the open architecture of the SLM system by enabling application-specific control algorithms to be downloaded and whole control loops to be changed dynamically as a result.

The deterministic nature of the ASIC protocol synchronises three controllers within any axis ie position interpolator, position/speed controller and the current loop. It also synchronises individual axes to a primary trigger and the whole system to within 50 ns. In order to eliminate 'jitter' on synchronisation the parameter passing channel is implemented within the protocol and a global hardware trigger facility is available which provides inter-axis synchronisation to within 10 µs.

'M'Ax does this in a number of ways. Firstly, it enables the OEM to offer more performance from his machine. To illustrate this: in a test with a laser cutting machine equipped with 'M'Ax 146 holes were cut in a period of one minute, each with a roundness accuracy of 50 µm. This compares with a total of 89 holes, with a roundness accuracy of 200 µm, for a conventional servo system over the same time period on the same machine.

Secondly, for typical three-axis applications, the MultiAx offers a unique solution. Three servo axes in one package slashes component and installation costs by reducing power cabling (3 to 1) and control cabling by 57%. The more axes that are employed the greater is the saving.

Thirdly, 'M'Ax is a purely digital system so it is much easier to set up. Axes coordination is much more precise, resulting in true synchronisation and the improvements in all-round performance this brings. In addition, much time and cost is saved because, uniquely, there is no requirement for the system builder to undertake the task of programming a motor map into the drive. This is done automatically by the intelligent SLM encoder. As a result the system user is able to switch on the drive system and get excellent performance immediately.

Finally, with cubicle space being expensive on modern M/Cs 'M'Ax's slim compact profile – it is one of the smallest servo drives on the market - allows OEMs to pack in many axes into the smallest possible space (six axes in a standard 600 mm cubicle).



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

A world first in maintenance
Motion Control & Drives
Lutz Pumpen has therefore developed a filling tool called Lutz Lube Drive, which considerably simplifies the maintenance process. The idea is that a commercial cordless screwdriver becomes the motor of a pump tube.

Read more...
The future of robotics
Motion Control & Drives
Research into robotics and autonomy uncovers some of the up-and-coming industrial uses and applications within the sector, including for automotives and logistics, as well as for personal and commercial use.

Read more...
Customised electromechanical systems for Africa’s toughest industrial environments
Motion Control & Drives
Hexagon Electrical, a South African-based manufacturer of specialised electromechanical equipment, is reinforcing its position as a leading custom solutions provider to the mining, utilities, industrial and renewable energy sectors.

Read more...
Epiroc strengthens productivity and sustainability
Motion Control & Drives
Epiroc is accelerating the transformation towards more productive and sustainable mining operations with the introduction of the new Minetruck MT22. The new 22-ton underground truck is designed for mining operations with small drift sizes, delivering increased effectiveness, reduced exhaust emissions, lower fuel consumption and extended service intervals.

Read more...
Hoist gives better load control
Motion Control & Drives
An important criterion for lifting equipment is that it is correctly loaded and balanced in order to avoid mechanical failures and accidents. More importantly, operator safety is enhanced as a result of correct load control, which reduces the possibility of damage to the materials and goods being lifted.

Read more...
PC-based control in window and door production
Beckhoff Automation Motion Control & Drives
Belgian machine builders CNC Solutions and Calvet are automating previously manual processes in aluminium window and door production. High-performance drive technology, motion control and electric cylinders from Beckhoff proved crucial in equipping the machine with the necessary finesse when pressing the window frames.

Read more...
World-class hoist maintenance
ABB South Africa Motion Control & Drives
In underground mining, hoists are among the most significant investments a company can make. ABB has developed ABB Care for Hoisting, designed to help mining companies transition from reactive or even preventive maintenance approaches to a truly predictive model, maximising hoist performance, extending asset life, and safeguarding operational continuity.

Read more...
Large-scale green hydrogen plant
Motion Control & Drives
As Europe’s first large-scale green hydrogen plant, Shell’s Holland Hydrogen 1 is a landmark renewable energy project. Mammoet was involved to plan and manage the road movements and key lifts that would bring the facility to life.

Read more...
Planetary gear units for high torque requirements
SEW-EURODRIVE Editor's Choice Motion Control & Drives
Packing a compact design, along with high torque and low-speed outputs, the new SEW PPK and SEW P2.e planetary gear units from SEW-EURODRIVE offer new capabilities in continuous heavy-duty applications where space is at a premium.

Read more...
Robotic filling systems for the pharmaceutical industry
Motion Control & Drives
Pharma Integration, a leading pharmaceutical manufacturer, aims to replace traditional mechanical filling lines with compact, fully automated systems that are 100% robot-driven using machines known as Azzurra. Their integrated Faulhaber drives play a crucial role in the fill-finish process, ensuring the highest precision and safety across multiple production steps.

Read more...









While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.




© Technews Publishing (Pty) Ltd | All Rights Reserved