Motion Simulator

Multi-processor Architecture

guarantees performance at a fixed update rate of 20kHz with 48-bit accuracy, for all axes . 

The MPU is a standard miniature Pentium-like PC that manages each SPii processor. The MPU handles high-level tasks, including axis profile generation, host/controller communication, user-program execution, and safety event handling.

SPii stands for ACS Motion Control second generation ASIC Servo Processor. The SPii ASIC is based on a 120MHz RISC core designed and optimized by ACS Motion Control for real time motion control algorithms. It combines all the peripherals required to implement a complete, high-performance, all digital motion control system. All of our standard and customized OEM SPiiPlus control products are based on the SPii processor.

Each SPii handles low-level tasks including:

Advanced real time algorithm and special filter execution
Digital encoder input up to 20 million counts per second
Analog Sin-Cos encoder input and interpolation up to a multiplication factor of 65,536\
Fast, high-rate Position Event Generator (PEG) to trigger external devices
Fast position registration (Mark) to capture position on input event
High resolution analog or PWM command generation to the drive
High Speed Synchronous Interface channel (HSSI) to manage fast communication with remote axes or I/O expansion modules

Nanometer Positioning & High Velocity

The SPiiPlus offers a powerful feature known as a Sin-Cos Encoder Multiplier. When nanometer axis position resolutions are required, users have usually been limited to expensive laser interferometer feedback systems. With the internal SPiiPlus Sin-Cos Encoder multiplier, users can use the much less expensive analog Sin-Cos encoder with 1Vptp differential outputs to achieve the required high resolution.

The maximum theoretical Sin-Cos encoder multiplication factor is 65,536. The maximum velocity is not dependant on the selected multiplication factor, and is limited to 250k sine periods per second. To achieve even higher frequencies please contact your ACS Motion Control sales representative.

The SPiiPlus PCI and linear drives were tested on a high performance XY table used for wafer inspection with Sin-Cos encoder resolutions of 4nm (250 lines per mm). Using a multiplication factor of 8,192, our engineers measured a jitter of ±2 encoder counts, which is equivalent to ~1nm. At this high resolution, the axis achieved velocities up to one meter per second.

Fast Settling, Low Jitter, Fine Velocity

The servo performance of an axis can be defined and measured by three main parameters: settling time, jitter (standstill when motor is under servo) and constant velocity.

With our advanced software tools including a four-channel soft-scope, these three parameters are easily monitored and analyzed.

Minimum Settling Time

Axis settling time has a direct impact on total machine throughput. With our 20kHz high-rate servo control loops, advanced control algorithms and professional analysis and adjustment tools, the settling time of an axis can be reduced to a minimum. Depending on specific application characteristics, a settling time of a few milliseconds is possible. By defining axis stabilization and duration windows, settling time can easily be monitored.

Minimal Jitter

Standstill jitter is a critical factor in many high-end applications like wafer inspection or precision inspection systems. Using the SPiiPlus 20kHz servo rate, Sin-Cos encoder multiplier and advanced control algorithms, jitter can be reduced down to ±1 feedback count. This low jitter can eliminate the need for mechanical brakes to hold the axis during standstill.

Fine Constant Velocity

Constant velocity is also a critical factor in scanning applications. With our advanced algorithms, including special torque ripple compensation (cogging), constant axis velocity can be significantly improved to less than 1% of the specified velocity. Our SPiiPlus products include a dedicated tool to accurately monitor the constant axis velocity.

Multi-axis Coordinated Motion & I/O Events

SPiiPlus motion controllers provide on-the-fly modification of any motion variable, highly flexible multi-axis synchronization, and I/O event management with sub-microsecond delay. Synchronization between virtual or physical axes can include master-slave, electronic gearing, cam motion, group (vector) motion and more.

The generated motion profile is updated each 1msec (as a default) with a new set-point per axis where the control loop is based on linear interpolation between two set points. These powerful capabilities together with the high 20kHz servo rate and sophisticated real-time control algorithms provide very smooth motion with minimal position (following) error.

Advantages:

• Easy implementation of any required synchronization or relation between axes
• Fast and accurate I/O event generation with sub-microsecond delay