Coordinating motion across three or more axes represents a significant challenge in industrial automation. While electronic gearing and camming handle basic synchronization, advanced robotics require a more sophisticated approach. Rockwell Automation’s Studio 5000 environment offers powerful “Coordinated Motion” features to solve these complex calculations. This technology allows developers to synchronize up to six axes simultaneously. Consequently, engineers can build custom articulated robots or complex gantries without external controllers.
Understanding the Shift from Joint to Cartesian Space
Most industrial robots rely on revolving joints that require precise angular calculations. However, programmers prefer working with X, Y, and Z coordinates, known as Cartesian or orthogonal space. To bridge this gap, the PLC must translate desired tool positions into individual joint movements. This process often involves complex “Reverse Kinematics” to ensure smooth translation between coordinate frames. Therefore, choosing the right coordinate system is the first critical step in multi-axis configuration.
Configuring Multi-Axis Systems in Studio 5000
Setting up a coordinated system is more intensive than standard motion grouping. First, you must create a “New Coordinated System” within your motion group in Studio 5000. The software then provides a wizard to define geometry, offsets, and maximum motion parameters. Moreover, the system supports at least two physical servos, while emulators typically allow three virtual axes. This foundation ensures that all related motors operate under a unified mathematical model.
Mastering PLC Logic and Movement Commands
Rockwell utilizes specific function blocks to drive coordinated motion effectively. For instance, the MCLM (Motion Coordinated Linear Move) handles straight-line travel between points. Meanwhile, the MCCM (Motion Coordinated Circular Move) executes 2D or 3D arcs. For highly specialized geometry like SCARA or Delta robots, engineers use the MCPM (Motion Coordinate Path Move). These blocks ensure that all joints reach their destination at the exact same moment.
Advantages Over Traditional Synchronized Motion
Coordinated motion differs significantly from simple electronic gearing. In a geared system, axes are strictly locked together. In a coordinated system, however, axes remain independent for individual commands when needed. You can execute a standard move on one axis without disrupting the others. As a result, the controller dynamically adjusts the speed of each axis. This ensures that the motor with the longest path determines the overall move duration.
Author Insight: The Democratization of Robotics
In my view, the integration of these advanced motion blocks directly into standard PLCs is a game-changer. Historically, building a six-axis robot required expensive, proprietary controllers. Now, high-speed industrial Ethernet like EtherNet/IP allows a standard PLC to manage these complex physics in real-time. For small to mid-sized manufacturers, this means they can build specialized “DIY” automation cells at a fraction of the cost. However, I recommend rigorous testing in a virtual environment before deploying these complex paths to live hardware.
Practical Application Scenario: The 3-Axis Servo Gantry
- The Setup:Â A gantry system with three servo axes mounted at right angles.
- The Implementation:Â Add all three axes to a single coordinated motion group.
- The Process:Â Use standard jog functions to “teach” the robot specific locations. Save these X, Y, and Z coordinates into a position array.
- The Result:Â Trigger the MCLM block to move between points. The gantry will follow a perfectly straight diagonal path rather than “stair-stepping” through individual moves.
