PLC CAM Table Switching for Motion Control

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

In existing motion control systems, switching between CAM tables requires stopping the driven shaft, resulting in wasted time, and there is a lack of efficient methods for rapid CAM table switching.

Innovation Solution

A computation unit in a programmable logic controller (PLC) is configured to execute motion control using a CAM table with displacements associated with each phase of an electronic cam, allowing for rapid switching between first and second CAM tables, with features like acceleration and deceleration limiting, smoothing filters, and high-order polynomial equations to ensure smooth transitions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If CAM table switching is implemented in conventional motion control systems, then the driven shaft must be stopped to switch tables, but this results in wasted time and reduced productivity

Engineering Contradiction:

ImproveCAM table switching capabilityVSAvoiddowntime during CAM table switching

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by pre-loading multiple CAM tables into the memory before switching is needed. The system maintains readiness of multiple CAM tables (first CAM table and second CAM table) in advance, allowing instantaneous switching without stopping the driven shaft. This eliminates the traditional requirement to halt the system before CAM table changes.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements dynamics by enabling dynamic switching between CAM tables during runtime without system interruption. The control unit can switch from the first CAM table to the second CAM table while the system is operating, making the switching process adaptive and flexible rather than static and interruptive.

Inventive Principle:

Principle #15Dynamics

2Productivity

If rapid CAM table switching is implemented, then productivity improves, but smoothness of transition and operational stability may deteriorate

Engineering Contradiction:

Improvespeed of CAM table switchingVSAvoidsmoothness of transition

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The control unit performs preliminary preparation by having multiple CAM tables pre-loaded and ready in memory before switching is required. This allows the system to switch tables rapidly without interruption while maintaining smooth transitions, as the next CAM table is already prepared and can be activated instantly without causing mechanical shock or instability.

Inventive Principle:

Principle #10Preliminary action

3Adaptability or versatility

If multiple CAM tables are stored and switched during execution, then adaptability improves, but device complexity increases

Engineering Contradiction:

Improveability to switch between multiple CAM tablesVSAvoidmemory and control unit configuration

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies universality by designing the control unit to handle multiple CAM tables through a unified control mechanism. The same control unit that executes the program can also manage switching between different CAM tables, making the system multi-functional without requiring separate dedicated hardware for each CAM table management task.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9869979B2Computation unit, output control method, and program

Publication Date: 2018.01.16 OMRON CORP

AI summary

A CPU unit of PLC executes a motion control and a sequence control. The CPU unit stores a control program for executing the motion control using a CAM table, and a first CAM table and a second CAM table. When a microprocessor receives a predetermined instruction during execution of the control program, the microprocessor switches the CAM table used in the execution of the control program from the first CAM table to the second CAM table. On the basis of the switching of the CAM table, the microprocessor outputs the execution results of the control program using the second CAM table to an apparatus to be controlled.