GHD Global Help Desk. Sequential programming with ATVlogic 03/2010

Transcription

1 GHD Global Help Desk Sequential programming with ATVlogic 03/2010

2 Table of contents 1. Introduction Sequential application example Grafcet description ATVlogic basic Grafcet step implementation Full ATVlogic program...8 Version : 00 of Page : 2/8

3 Pictograms Purpose of the chapter or paragraph. Additional information or remark. Definition type information. Version : 00 of Page : 3/8

4 1. Introduction ATVlogic is originally designed for basic Boolean calculations inside ATV32 drive. The problem is that Boolean operations cannot handle easily sequential operations. That is why this application note describes how to implement sequential programs with ATVlogic, using the ATVlogic function blocks library. Version : 00 of Page : 4/8

5 2. Sequential application example Here, a rotary table is driven by a variable speed drive. This table has to be stopped according to marks placed on it. To ensure stop precision, the speed is reduced thanks to slow down marks. The table remains stopped during 3 seconds, and then the cycle starts again from the beginning. The first cycle is started by a push-button. Sensor Rotary table Start pushbutton Stop mark Slow down mark Sequential application example It is possible to manage this application only with Boolean operations, but it can be tricky. Using sequential programming is much easier. In this case, SFC programming language has to be used. Version : 00 of Page : 5/8

6 3. Grafcet description Grafcet is used to describe sequential applications. The following Grafcet describes the behavior of the rotary table: 0 Wait Start push-button is pressed 1 Run at high speed Slowdown mark is detected 2 Run at low speed Stop mark is detected 3 Wait 3 seconds timer is elapsed Rotary table application Grafcet Following this Grafcet, this application can be implemented directly by using SFC programming language, for example with SoCollaborative or SoMachine. But ATVlogic cannot be programmed directly with SFC. The next pages describe how to program SFC-like applications with ATVlogic. Version : 00 of Page : 6/8

7 4. ATVlogic basic Grafcet step implementation This basic Grafcet step is used to build any chart: Wire coming from the previous step Step Action Transition condition Wire to the next step Basic Grafcet step The basic Grafcet step can be implemented in ATVlogic by using only 1 RS flip-flop and 1 AND gate: Wire coming from the previous step Transition condition: if TRUE, then next step is activated Action: TRUE if this step is active Wire to the next step Grafcet step programmed with ATVlogic Version : 00 of Page : 7/8

8 5. Full ATVlogic program The rotary table program is built by assembling steps, by connecting virtual inputs to transitions and steps to virtual outputs. The backward link from step 3 to step 1 is ensured by an OR gate: Initialisation circuitry to activate the 1 st step Input connected to start pushbutton First step OR gate used to branch 2 wires Output connected to forward command Input connected to sensor Output connected to preset speed 3 s timer Rotary table ATVlogic program For this application, LSP has to be set higher than 0 Hz: LSP defines the table speed between the slowdown mark and the stop mark. Preset speed is used for the high speed rotation. Because this program requires 14 blocks, it cannot be executed in a synchronous way in PRE and/or POST task. Executing these 14 blocks requires 232 µs and the duration of PRE + POST tasks has to be shorter than 200 µs. AUX task should be used. This example does not take into account all of initial possible states: for example, if the sensor is between the slow down and the stop mark when the push-button starts the first cycle, the high speed and slow speed phases will be inverted. The solution is to use 1 sensor dedicated to slow down marks detection and a 2 nd sensor for stop marks. Version : 00 of Page : 8/8