Motion Control Advances Target Robotics

Integrated, Precision Solutions

Motion control technology for robotics continues to advance, as chip- and board-level solutions evolve to meet new demands. These involve a blending of precise analog technologies to control position, torque and speed with signal processing to enable accurate, real-time motor control.

By Jeff Child, Editor-in-Chief

Robotics is one of those unique market segments that qualifies as both old and new. Industrial robotics is a mature, established field. And the motion control, motor control, servo controllers and all the associated support technology used in industrial robots make up an established ecosystem. At the same time, new advances and innovations in these kinds of robotics are happening at a dynamic pace as robotic systems are tasked to do more complex functions, operate with more autonomy and upgrade to more integrated electronics.

To keep up with the demands of industrial robotic systems, vendors of motion- and motor-control chips and boards are offering a wide range of solutions ranging from compact servo controllers to industrial-focused microcontrollers to complete development kits.

Precision Robotics

Exemplifying these trends, among the latest solutions from STMicroelectronics is its STSPIN820 motion control chip (Figure 1) designed to enable the fine motor skills of precision robots. Industrial robotics including 3D printing have greatly enhanced accuracy and throughput in recent years. 3D printers can produce parts with complex shapes, quickly and accurately and are becoming more and more affordable, for consumer and professional uses from prototyping to production. The STSPIN820 IC enables the next generations of stepper-motor-based robots to achieve even greater smoothness and silence, with smaller size, greater precision and lower power consumption.

Figure 1
The STSPIN820 motion control chip is designed to enable the fine motor skills of precision robots. For example, with its high-speed inputs and precise micro-stepping algorithm, it can turn a motor by a fraction of a degree to move a 3D printer’s head at a speed of more than 500 mm/s.

With its high-speed inputs and precise micro-stepping algorithm, it can turn a motor by a fraction of a degree to move a 3D printer’s head at a speed of more than 500 mm/s, with submicron precision to create parts very quickly and with incredible surface finish. Or it can control extremely precise movements like sample loading, capping/decapping and storage/retrieval in next-generation clinical automation systems.

The device measures 4 mm x 4 mm and contains both the control intelligence and fully protected power components—rated 45 V and 500 mΩ RDS (ON)—for driving the motor. The company claims it as the world’s smallest all-in-one high-precision controller. The STSPIN820 is a dedicated stepper-motor driver with 256-microstep resolution. It operates from a supply voltage between 7 V and 45 V, simplifying design-in for a wide range of applications. The maximum output RMS current of 1.5 A gives designers flexibility to satisfy various power and torque requirements.

The STSPIN820 leverages ST’s proprietary Smart Power technology, which integrates motor-control logic featuring a high-precision micro-stepping algorithm with a low-RDS(ON) fully protected power stage in a single device. It provides familiar step-clock and direction-input pins. This simplifies connection to a host processor or microcontroller.

Interface Support

The MCU/MPU line from Renesas Electronics designed for industrial control and robotics is its RZ/T1 family. Last fall, the company added a version of the RZ/T1 that provides a HIPERFACE DSL digital encoder interface for AC servo applications. The support of HIPERFACE DSL for RZ/T1 reduces a system designer’s bill-of-materials (BOM) cost and enables faster time-to-market.

HIPERFACE DSL is an industry-leading interface provided by SICK STEGMANN GmbH, and uses the familiar RS485 cabling with a transmission rate of 9.375 mega baud rate. The data is transmitted in synchronization with the drive cycle, and the cable between the drive electronic and feedback system can be up to 100 m in length.
The RZ/T1 architecture includes the Arm Cortex-R4 processor with a dual precision floating-point unit (FPU) operating at up to 600 MHz. It provides real-time processing, tightly-coupled memory, high-speed analog to support dual servo motors and network connectivity for distributed motion that matches the needs of precise AC servo drive applications.

Figure 2
The RZ/T1 Motion Control Solution Kit includes an RZ/T1 CPU card and a dual channel 3-phase inverter to support dual channel servo motor control with current and position feedback.

The RZ/T1 already supports other leading encoder interfaces including EnDat 2.2, BiSS-C, Tamagawa and A-format. These digital, bidirectional interfaces provide precise position values from absolute encoders. Instead of using a separate FPGA or ASIC. Integrating these encoder interfaces on the RZ/T1 reduces the component count and cuts system costs.

With the added HIPERFACE DSL functionality, the RZ/T1 now supports most of the leading encoder interfaces, and with its unique configurable encoder interface, it simplifies swapping different encoders interfaces from a single device platform. Renesas supports the RZ/T1 family of devices with its RZ/T1 Motion Control Solution Kit, a complete hardware and software solution for the Renesas RZ/T1 MPU (Figure 2). The kit includes an RZ/T1 CPU card, and a dual channel 3-phase inverter to support dual channel servo motor
control with current and position feedback.. …

Read the full article in the September 338 issue of Circuit Cellar

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