07-18-2015 11:11 PM
dear all,
I would like to know if it is possible to use LabVIEW to control and syncronize the operation of a conveyor belt that feeds material into a hydraulic press.
If this is so, what would be required?
We need to be able to experiment and change the operation parameters until we find the "sweet spot"
example of parameters to change:
1. connveyor belt speed, from 8 m/s to 3,3 m/s
2. hydraulic circuit parameters:
- piston stroke
- relieve valve set pressure: from 2500 psi down to 2200 pis
these are just examples.
any comments / suggestions are appreciated
alvaro
07-19-2015 08:23 AM
alvaro,
Yes, it is possible. LabVIEW is a programming language. If you have or can obtain suitable interfaces between the computer and the conveyor belt speed control and the hydraulic controller, then you can do this.
Many motor speed controllers have an analog voltage input, a current input (4-20 mA), or a serial port communications input to set the speed. Many general prupose DAQ devices have voltage outputs (analog out). Other devices have current outputs. USB and PCI to serial port interfaces are readily available.
Similarly, you need to determine how the hydraulic parameters are controlled and select suitable interfaces to the computer.
Without more details on your equipment it is not feasible to be more specific about what you will need.
Other considerations:
- Safety: Do you need to monitor limit switches or other sensors?
What happens if the computer fails while the motor or hydraulics are still running?
What happens if either the motor or the hydaulics fail while the computer and the other part are still running?
- Control: What kinds of speed sensors and pressure sensors are you using?
How fast or how often do you need to change speed or pressure?
How fast do the mechanical/fluid systems respond to changes in setpoints?
How much overshoot or other transient behavior can the system tolerate?
How accurate do the speeds and pressures need to be?
The answers to these questions will determine whether you might need a PLC for the basic control with LV monitoring, a LV real-time system, or a LV desk-top system, or some combination.
Lynn
07-19-2015 12:25 PM
thank you Lynn,
you made me start thinking of issues I had not considered.
my answers to your questions below.
I must say this is the first time I work on a project that includes control / automation.
- Safety:
Do you need to monitor limit switches or other sensors? yes
What happens if the computer fails while the motor or hydraulics are still running? the system needs to stop
What happens if either the motor or the hydaulics fail while the computer and the other part are still running? the system needs to stop
- Control:
What kinds of speed sensors and pressure sensors are you using?
none at the moment, we are just beginning to work on the project
what kind should we use?
How fast or how often do you need to change speed or pressure?
initially we will have to experiment with the operation parameters until we find the most efficient configuration (the sweet spot: belt speed, stroke, hold time, etc) for every material.
How fast do the mechanical/fluid systems respond to changes in setpoints?
If the transition from one set of parameters to the next happens in 3-5 seconds that would be acceptable
How much overshoot or other transient behavior can the system tolerate?
belt speed: belt set point + / - 0,5 m/s
expected belt speed: 2-7 m/s
hydraulic parameters: hydraulic pressure set point: (2500 psi) +/- 50 psi
expected hydraulic pressure: 2500-2600 psi
How accurate do the speeds and pressures need to be?
belt speed: belt set point + / - 0,5 m/s
hydraulic parameters: hydraulic pressure set point: (2500 psi) +/- 50 psi
The answers to these questions will determine whether you might need a PLC for the basic control with LV monitoring, a LV real-time system, or a LV desk-top system, or some combination.
does it sound like I need a PLC?
I need to be able to play around with the machine, time it (calculate throughput, material recovery, etc) and find the "sweet spot" for each of the different materials that we want to process.
we need to be able to have a set of parameters for every material.
example:
material A (belt speed 1, hydraulic pressure 1, hydraulic pressure hold time 1),
material B (belt speed 2, hydraulic presssure 1, hydraulic pressure hold time 3),
material C (belt speed 3, hydraulic pressure 2, hydraulic pressure hold time 3),
any thoughts, suggestions are appreciated, regards,
thank you
alvaro
07-19-2015 04:48 PM
Sounds like a good application for cRIO, which involves a LabVIEW RealTime and a LabVIEW FPGA in a single chassis and then your IO is determined by C Series modules that you put inside of the cRIO chassis. My company does a lot of control applications. If you want help with this application, send me a PM with your information and we can start talks.
07-19-2015 04:56 PM
alvaro,
When you answered "the system needs to stop", that shouts that a standard desktop computer will not be acceptable for this application. A PLC is probably the easiest way to get the safety issues covered properly. Some standalone realtime systems can also be acceptable, but it sounds like you have little experience in this area so the learning curve for a PLC might be faster.
My recommendation is that you find a consultant experienced with factory automation who can advise you on the overall architecture of the system, the types of sensors and controllers needed, the safety factors, and possibly other important but not obvious details. Consider the cost of a crashed system or an injured operator, as well as the time it will take you to learn these things, against the fee you would pay the consultant.
Lynn