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Hydraulic axis Speed control

Created by: Kaltron at: 11/4/2014 12:01 PM (8 Replies)

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11/4/2014 12:01 PM	Rate (0)
Kaltron Posts: 3 Rating: (0)	I need to do speed control on a hydraulic winch. I will be using the 315T CPU with analogue output as speed command to the proportional valve that will turn the winch.the system also has a absolute profibus encoder for speed feedback. I configured the system in the S7T Config and programmed the MC_Power,MC_MoveVelocity, MC_Halt in my step 7 program. I am able to start and stop the axis. I need to control the winch with a proportional Joystick where the speed of the winch must be proportional to the position of the joystick i.e the further the joystick is pressed forward the faster the winch will turn. with _MoveVelocity i can only specify a fixed setpoint for the speed. how do i go about to do the speed control with a variable speed input?
Kaltron Posts: 3 Rating: (0)
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11/4/2014 12:11 PM	Rate (0)
casajr Posts: 153 Rating: (8)	Do a speed change detect and continuously switch the enable on the MC_Velocity command. I would use MC_Jog instead, but that's just me. Or, just write you speed reference directly to your analog output and bypass the TO.
casajr Posts: 153 Rating: (8)	Last edited by: casajr at: 11/4/2014 12:16 PM
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11/4/2014 12:30 PM	Rate (0)
Technology Team Platinum Expert Joined: 10/11/2006 Last visit: 4/17/2025 Posts: 6008 Rating: (827)	Hello, The TO has a variable "override.velocity". You change the value depending on the position of the joystick in your program. So you can set a speed command with fix speed and manipulate it via the override.
	With best regards, Technology Team Application consulting and pre sales support for SINAMICS, SIMATIC Technology, SIMOTION, SIMOTICS and MOTION CONNECT
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11/4/2014 12:40 PM	Rate (0)
casajr Posts: 153 Rating: (8)	True, but the OP is using PLCopen commands.
casajr Posts: 153 Rating: (8)
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11/4/2014 12:49 PM	Rate (0)
Kaltron Posts: 3 Rating: (0)	How can I use the override.velocity from my step7 program? is there another way of controlling the axis other than with PLCopen commands?
Kaltron Posts: 3 Rating: (0)
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11/4/2014 12:54 PM	Rate (0)
Kaltron Posts: 3 Rating: (0)	I don’t have a MC_jog FB in the S7-Tech lib supplied with the software. Also i need to control the speed, a 20% signal to the valve will have a different winch speed with different loads so i cannot just move the speed command to the analogue value. The winch needs to do Active heave control so the speed accuracy is critical.
Kaltron Posts: 3 Rating: (0)
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11/4/2014 1:52 PM	Rate (0)
Technology Team Platinum Expert Joined: 10/11/2006 Last visit: 4/17/2025 Posts: 6008 Rating: (827)	Hello, your valve have no linear characteristic. Maybe this can help you. http://support.automation.siemens.com/WW/view/en/27731588 When you reallyuse 315T CPU with technology, the necessary commands are available. 6.2 Technology functions - Single axes 6.2.11.2 MC_MoveVelocity - Example - "Override motion" ..................................................................... 6.8.5.2 MC_WriteParameter - Example - "Override" http://support.automation.siemens.com/WW/view/en/30119663
	With best regards, Technology Team Application consulting and pre sales support for SINAMICS, SIMATIC Technology, SIMOTION, SIMOTICS and MOTION CONNECT
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11/10/2014 11:17 PM	Rate (1)
DavidBrown Gold Member Joined: 6/29/2012 Last visit: 12/25/2023 Posts: 975 Rating: (9)	As in my case the joystick can be moved in both forward and reverse direction (to move the load in forward and reverse direction with speed proportional to joystick input) and because when the joystick is at neutral position, a the position of the load has to be hold with position control, and because the load may only move to a limited position in both directions, I am thinking of calling every cycle the _Pos technology function, where I change the direction depending on the direction of the joystick and where i change the velocity depending on the level of the joystick. When the joystick is pushed forward I would put my position setpoint at the positive limit of the load, and vice versa. If the joystick is at neutral position, I would set my position setpoint at the last actual position when the joystick was put at neutral position and the load was at standstill. Only thing I should care about is not giving the _Pos function a zero speed setpoint. I suppose calling the _pos function every cycle (background or maybe Ipo) would cause no problems?

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11/11/2014 9:29 AM	Rate (0)
Technology Team Platinum Expert Joined: 10/11/2006 Last visit: 4/17/2025 Posts: 6008 Rating: (827)	Hello, I would not call the _pos function in every cycle because the load of the system. Do a If-condition depending on the speed change in front of the command, so that you call the function not in every cycle. Maybe at smaller speeds in 0,5 1/min steps and at higher speeds in 5 1/min steps, depending on your application. And If setpoint is 0 use a stop command. More elegant would be: overrride.velocity:= factor* abs(setpoint); If setpoint 0 and stop_command = falsethen _stop pos_positive:= false; pos_negative:= false; stop_command := ftrue; end_if; If setpoint > 0,1 and pos_positive = falsethen _pos absolute with max. possible positive position pos_positive:= true; pos_negative:= false; stop_command := false; end_if; If setpoint < - 0,1 and pos_negative = false then _pos absolute with max. possible negative position pos_negative:= true; pos_positive:= false stop_command := false; end_if;
	With best regards, Technology Team Application consulting and pre sales support for SINAMICS, SIMATIC Technology, SIMOTION, SIMOTICS and MOTION CONNECT
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