APPLICATION NOTE Decentralised EtherCAT motion system offers build time benefits: AB Dynamics’ high-end vehicle K&C test systems include Kollmorgen AKD-N servo drives from Heason Technology

AB Dynamics’ Suspension Parameter Measurement Machine (SPMM) is used extensively by global vehicle manufacturers, vehicle standards test houses and tier-one component suppliers for the measurement of vehicle kinematics and compliance (K&C) data as part of progressive R&D and for production quality control. The SPMM is a 19-axis motion controlled machine that makes precise measurements of vehicle body and component deflections whilst loading the vehicle. It delivers a complete and faithful simulation of on-road vehicle behaviour and includes a comprehensive range of upgrades and options including Vision Systems, Moment of Inertia (MIMS) and Centre of Gravity (C of G) measurement capability. Heason Technology - the designer, manufacturer and distributor of world-class motion solutions – is a long-term support and supply partner for motion control components specified by Bradford on Avon based AB Dynamics. The next-generation SPMM, which has unrivalled measurement accuracy and improved performance utilises the Heason supplied AKD-N series EtherCAT-enabled decentralised servo drives from its distribution partner Kollmorgen. This has significantly improved the SPMM’s control system design by allowing a more distributed and modular design approach to be adopted. This has greatly reduced the hardware used in the system and the number of cables running from the SPMM to the control cabinet.

Image: AB Dynamics’ next-generation Suspension Parameter Measurement Machine (SPMM 5000)

AB Dynamics’ SPMM 5000

The moving body platform of AB Dynamics’ SPMM 5000 features a central table which is precisely motion controlled via electric servo actuators in six degrees of freedom. This enables a combination of roll, pitch, bounce and yaw motion to be applied to the vehicle body during K&C and MIMS testing. The design geometry of the machine ensures that the ground plane (which replicates the road) is fixed during cornering and braking simulations. Each wheel station includes additional motion axes that generate X, Y and Delta forces at each wheel contact patch. By utilising high accuracy multi-component piezoelectric load cell assemblies below each wheel and a high accuracy “dynamic arm” wheel position measurement system, the SPMM 5000 is able to precisely measure all of the wheel forces and moments and the X, Y, Z, steer, camber and spin motion of the wheel centre.

All of the motion axes on the machine (up to 18 for a four-wheel station SPMM 5000) include Heason supplied AKD-N and AKD-P EtherCAT enabled decentralised servo drives. In addition, the Delta axes include Heason developed servo actuators based around TwinSpin^® precision gear reducers from Spinea – also a distribution partner for the West-Sussex based motion specialist. This unique gear reduction solution integrates heavy-duty radial-axial bearings with a trochoidal gear reduction system into a single compact unit, that removes the need for separate load support bearings or mechanics. In addition, a single AKD-N servo drive with EtherCAT is directly coupled to and provides simulation of the vehicle’s steering system. 

The SPMM 5000’s measurement systems and algorithms provide suspension engineers with an essential aid to the thorough understanding of a vehicles performance in terms of ride, steering and handling.

Kollmorgen AKD-N decentralised motion systems

Previous SPMM machine designs have also typically used up to 19 motion axes, however with centralised (cabinet-installed) motion control, the need to house high-power servo drives and power supplies centrally necessitated large air-conditioned control cabinets with the requisite motor power + feedback cable management systems installed over long runs across the large area of the machine, which has nominal dimensions in the region of 7.5 x 4.5 x 2.5 metres. With continuous machine power requirements up to 15kVA, the associated commissioning, inventory and component burden for the centralised design concept combines for a significant simplification in system wiring.

 

Image: Kollmorgen AKD-N decentralised servo drives and power supply

With each AKD-N servo drive located and connected close to its motor, and with DC power daisy-chained around the machine to each drive, significant savings in installation time has led to faster assembly and site commissioning times. Simplified wiring and cable management means AB Dynamics’ modular machine design requires less hardware, spares inventory, and field upgrades, for example two to four wheel set-ups are more easily achieved. The new SPMM 5000, without the need for a large control cabinet, also requires a smaller footprint which is an important factor for production test area installation.

If the benefit of reduced commissioning and build time sounds compelling, then it is even more interesting to note that Kollmorgen’s AKD-N boasts a single hybrid cable connection for motor power and its Hiperface DSL enabled absolute encoder feedback (from a wide range of feedback options). Furthermore, the single cable philosophy extends to the servo drive power and fieldbus where an 11 mm diameter hybrid cable is used for the DC-bus and EtherCAT connection. It is also possible to run Safe Torque Off (STO) safety through this single cable. These factors combine for even less machine wiring than other manufacturers’ decentralised drives that require separate drive power and fieldbus connections as well as separate motor power and encoder cabling.

As a decentralised system, Kollmorgen’s AKD-N series servo drives perfectly suit AB Dynamics’ wide range of system configuration and measurement options it offers the SPMM 5000. A single AKD-C power supply may be used for up to 16 AKD-N drives and may also be machine mounted for convenience. Individual AKD-N drives cover a power range up to 4 kW and may be combined with centralised AKD series EtherCAT drives where even higher powers are required.

EtherCAT fieldbus

Kollmorgen’s AKD-N series decentralised drives have a proven record not just for lower machine complexity but also for the high-speed synchronisation offered by the EtherCAT industry standard fieldbus. The real-time deterministic fieldbus system with low communication jitter is particularly suited to automation applications requiring short data update times. The freely scalable Plug and Play solution allows additional motion axes, sensors or machine I/O to be readily added to ensure the highest degree of design freedom for machine building. Commissioning and servo tuning is fast and straightforward with the graphical-based Kollmorgen Workbench^®. Well proven for other vehicle simulation platforms and high-speed automation applications such as packaging, processing and assembly machinery, the AKD-N decentralised drives used for the SPMM seamlessly perform in concert with AB Dynamics’ own EtherCAT master-based hardware and software system. Complex kinematics algorithms generate a series of motor current (torque) demands to each individual axis in real-time and in close synchronisation with all the sensor measurement data.

Heason Technology – a long-term relationship supplier

Heason Technology’s engineers work closely with its customers, providing motion control expertise as well as supporting and delivering a wide range of motion components in its role as a UK distribution partner for a select number of globally recognised motion control companies. In addition, the West Sussex-based motion systems integrator has a comprehensive in-house design and build capability that includes custom-built mechanics with servo, stepper and automation controls for the most demanding applications across industry and research.

For further information, please email This email address is being protected from spambots. You need JavaScript enabled to view it."This email address is being protected from spambots. You need JavaScript enabled to view it. or call +44 (0) 1403 792 300.

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