Mark Roberts Motion Control source hexapod positioning system from Heason Technology
14 January 2020
Mark Roberts Motion Control (MRMC), a Nikon Company, is an award winning designer and manufacturer of motion control hardware and software widely used in the film, television and professional photography industries. Its extensive range of camera robot solutions enable high speed, pixel accurate and highly repeatable compound movement that is essential in enabling technology for the special effects and visual imagery we all enjoy today. As part of MRMC's impressive array of 'motion rigs', Heason Technology has recently supplied design expertise and components for an EtherCAT controlled 6-axis hexapod that is used as a model mover. With its 1500 kg payload, MRMC's servo motor driven 'motion base' precisely enables objects or even actors to move in any linear and rotational direction in a volume of approximately 0.7 m3 - to create the illusion of motion when paired with its sophisticated Flair software.
Heason Technology worked closely with MRMC from the conceptual phase of the motion base project and contributed its motion systems expertise through the design and specification for the hexapod mechanics and drives including its load and performance calculations. The motion specialist also supplied most of the proprietary and custom designed components for the project that was assembled at MRMC's Surrey-UK facility. Heason Technology combines its own design and build capability with motion products, components and systems from a select group of globally recognised distribution partners. Its systems integration service is backed by a sales application team and extensive in-house motion engineering support including sophisticated 3D CAD and motion simulation software. For the motion base project Heason supplied precision linear actuators from its distribution partner Thomson Industries as well as brushless servo motors, EtherCAT ready servo drives and associated accessories from Kollmorgen.
With its six precision linear actuators arranged in a Stewart Platform geometry, MRMC's motion base produces the synchronised compound movement in six-degrees-of-freedom (X, Y, Z, pitch, yaw and roll) that its Flair software determines as a real-time trajectory seen from a camera lens or from any other point in space for a specific shooting sequence. The PC-based software calculates the actual leg length positions required for each actuator which is transferred into each axis' brushless servo drive via an EtherCAT master. With the ability to create and replay motion sequences with high repeatability and precise accuracy, complete scenes can be composed where actors or models are filmed against a green screen for example, to give the appearance of fast and exciting movement. In a second operational mode, the motion base can be controlled from a manually operated miniature scale replica of the hexapod that mimics the position of six high-precision linear encoders. Similar to a joystick controller, motion sequences can be loaded, adjusted and replayed by MRMC's Flair software.
The Tollo T90 series actuators used on the MRMC Motion Base feature preloaded ballscrews for very low lost motion. Fully sealed and quiet in operation, they each provide 700 mm travel (up to 2 m available in frame size T90) with an anti-rotation mechanism for the extension tube and a T-Slot housing design that accommodates datum/overtravel sensors. Parallel motor mounts were specified to conserve space on the hexapod frame. The six actuators are symmetrically mounted using a Heason designed clevis mount arrangement that ensures minimal hysteresis. The T90 series is capable of speeds up to 2 m/sec and offers a load capability of up to 40 KN.
Each actuator is then fitted with a Kollmorgen high-torque density AKM2G series servo motor with Hiperface feedback that requires only a single cable for motor and encoder power simplifying installation time and cost. Fitted with a spring applied brake to ensure the actuator's position is locked when power is removed, the motor is capable of delivering up to 30% higher continuous torque compared to competitive motors of equivalent size and easily powers the motion base at high speed and with high precision.
A variant of Kollmorgen's AKD-Basic advanced servo drives completes the motion system. MRMC's leg length and millisecond based time coordinates are transferred to the servo drive through its EtherCAT interface. The 12A continuous/30A peak current drives, supplied in a 19 inch rack with power supplies and all components for three-phase operation were fully tested and pre-configured by Heason. Installation was made easy with the aforementioned single cable package, simplifying the cable management between the control cabinet and the servo motors.
Heason Technology's long list of application success spans demanding industrial and scientific research motion control and positioning solutions for military & aerospace test systems, medical & life sciences, industrial production and test, packaging automation, marine & automotive engineering and more. Heason excels in specialist and challenging application areas such as synchrotron, imaging & photonics and UHV vacuum positioning systems where innovative integration of motion components and specially selected and prepared materials are often essential design requirements.
For more information, please contact:
Motion Solutions Centre
Spring Copse Business Park
Tel: +44 (0) 1403 792 317