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Hello,
I work for a manufacturer in the precast concrete industry. I had to control the system shown in the video:
I did that from ground (including CAD processing from production data to spreading plan, already few thousands codelines...) using a IPC/PLC with windows7 CE inside.
I have a problem of accuracy, because my sensors are very slow.
The position od the trolley is measured with laser telemeter and the concrete weight in the container by a weighing scale. The both have a sampling time of 15 ms. I need to derivate the position and the weight to compute the speed and the concrete flow. As the signals have some noises, using a filter I can't have good signals below 200 ms... Which gives a 5 Hz control, not good.
I thought to use a PID controller for the both actuators (the trolley uses direct electric motor through inverters and the concrete flow uses a feed screw in the container, with inverter too), but seeing this sampling time, I gave up.
The current control law is as follow:
My spreading gives me a kg to spread per mm-linear (kgmmFactor), so using this element and the Flow I measure, I set the speed:
TargetSpeed = Flow / kgmmFactor
The feeding screw uses a easier law, 100% - TrolleySpeed. When trolley drives at end speed the feedscrew goes slow and when trolley drives slow the feedscrew runs with high speed.
The problem is when the concrete spreader starts above a slab, there is always a lag and the first seconds give a little mound at the start position, while running always is fine...
Do you have an idea to make this process better?
I think I'm stuck with the sensors speed but I can't go faster.
Thanks!
I work for a manufacturer in the precast concrete industry. I had to control the system shown in the video:
I did that from ground (including CAD processing from production data to spreading plan, already few thousands codelines...) using a IPC/PLC with windows7 CE inside.
I have a problem of accuracy, because my sensors are very slow.
The position od the trolley is measured with laser telemeter and the concrete weight in the container by a weighing scale. The both have a sampling time of 15 ms. I need to derivate the position and the weight to compute the speed and the concrete flow. As the signals have some noises, using a filter I can't have good signals below 200 ms... Which gives a 5 Hz control, not good.
I thought to use a PID controller for the both actuators (the trolley uses direct electric motor through inverters and the concrete flow uses a feed screw in the container, with inverter too), but seeing this sampling time, I gave up.
The current control law is as follow:
My spreading gives me a kg to spread per mm-linear (kgmmFactor), so using this element and the Flow I measure, I set the speed:
TargetSpeed = Flow / kgmmFactor
The feeding screw uses a easier law, 100% - TrolleySpeed. When trolley drives at end speed the feedscrew goes slow and when trolley drives slow the feedscrew runs with high speed.
The problem is when the concrete spreader starts above a slab, there is always a lag and the first seconds give a little mound at the start position, while running always is fine...
Do you have an idea to make this process better?
I think I'm stuck with the sensors speed but I can't go faster.
Thanks!
