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CAN Network Adjusted for Advanced Motion Control

CAN Network Adjusted for Advanced Motion Control

The goal for Animatics Corp. of connecting its new Class 5 SmartMotors over a standard CAN network without the need for a dedicated master, allowing them to communicate on an equal footing and share all information and processing resources available on the network has been achieved. An array of these integrated servos can now act as a parallel-processing system capable of multi-axis coordinated motion, high-speed contouring, electronic camming and gearing.

How the company achieved this by adapting the industry-standard CAN network is a key point in Animatics' system design philosophy.

CAN Network Adjusted for Advanced Motion Control

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Leveraging an Industry Standard

"CAN is amazing technology that provides speed up to a megabit and a hardware infrastructure to decode messages and accelerate system performance, plus built-in arbitration and data collision features that create an excellent interface," says Robert Bigler, CEO of Animatics Corp.

Bigler says that to use CAN as an industrial network, the choices for a system designer are to use either CANopen and DeviceNet, both of which are widely recognized network protocols. The system architecture of each protocol uses a master and slave setup, but both still use a centralized control approach at their core. Initially, Animatics set out to use CANopen for advanced motion control networking by extending it.

"But we couldn't break through the master-slave mentality, so we had to create our own protocol which we call Combitronic," Bigler says.

Combitronic technology uses a CAN serial port to join Animatics' SmartMotor servos in a system so that any motor's program can read, write or control any other motor by tagging a local variable or command with the other motor's CAN address. The result is that a group of integrated servos become one multi-tasking, data-sharing system without writing a single line of communications code or requiring detailed knowledge of the CAN protocol.

This advancement allows any single axis to act as master to other axes in the system. Each servo is able to access and control all of the motion parameters and I/O in other servo motors. Any axis can use inputs or status registers in any other axis to trigger motion with sub-millisecond response times, exceeding the abilities of most PLCs to coordinate motion and I/O together.

CAN Network Adjusted for Advanced Motion Control

To leverage the Combitronic capabilities, a new class of commands has been added to the Class 5 SmartMotors that create multiple-axis coordinated motion accessible through one line of code executed in any of the contributing motors. First, the programmer sets a desired "path" velocity and acceleration, and then issues multiple positions and pertinent axis numbers for a completely coordinated move resulting in straight-line motion along the direct path.

Camming and contouring functions have dual trajectory capabilities, so users can add a relative motion on top of cam or contour motions. If there is material on a conveyor and a gantry is being used to synchronize its motion with a moving frame of reference such as a conveyor, users can set up a following relationship with the conveyor and perform the motion task in the coordinate system of the conveyor as it is moving.

The system is also able to perform other advanced motion functions such as curve fitting capable of adjusting the data set and maintaining system accuracy.

Motor Control

Class5 SmartMotors range from a Size 17, or 1.7-inch motor, up to more than 1 hp and torque up to 700 oz-inch. Each motor offers seven built-in I/O points, and an optional 10 I/O points can be added.

"With 10 motors in a system, there can be up to 170 I/O in the system, and program execution speed is several times faster than in the past. Many applications don't need a PLC in the machine," says Bigler.

Bigler adds that Combitronic provides the benefits of both centralized and distributed control by offering a distributed system where the user gets to write one program. Users typically favor centralized control because they can write one program that controls everything, which is easier to maintain. Distributed control is an advantage when parts of the machine are doing different functions, and users don't need to write a complicated program that is multi-tasking between the different tasks.

"Whether the application is single- or multi-axis, our customers love that they don't need the PLC and need just one controller and one program with all of that processing power," says Bigler.

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