Controlling a vacuum system comprising a vacuum generator arrangement
The invention relates to energy saving in vacuum systems by means of a method and a controller enabling to consider the fluctuation in system-pressure of a system by determining a maximum system-pressure S 2 H and a minimum system-pressure S 2 h for each working cycle W C based on a determined target system-pressure p n − and a pre-set system-pressure p 0 − for the current working cycle W Cn (n=1, 2, 3, . . . ). The method is especially adapted to fluctuations in system-pressure level of a vacuum system comprising a vacuum gripper tool.
1. A method for automatic pressure level determination and adaptation enabling energy saving in working cycles in a vacuum system operating a vacuum gripper tool for transportation of objects, said vacuum system comprises a vacuum generator arrangement driven by a compressed air flow, wherein the vacuum generator arrangement via a vacuum chamber being part of the vacuum system is arranged to be brought in flow connection with the vacuum gripper tools, in order to supply vacuum to the vacuum gripper in result of the compressed air flow, wherein a pressure sensor for monitoring a system-pressure p − (t) is arranged inside the vacuum chamber; and a vacuum system controller being electrically connected to a main controller, wherein the vacuum system controller is arranged to control and communicate with the vacuum generator arrangement and communicate with the pressure sensor, and the vacuum system controller is arranged to monitor the measured system-pressure p − (t) continuously, wherein the vacuum system controller further is capable to calculate a system-pressure time derivative D(t)=dp − /dt during the working cycles, wherein the method comprises the steps of:
determining at start-up of a working cycle value D 0 of the system-pressure time derivative at a pre-set system-pressure p 0 − ;
calculating value D target of target system-pressure time derivative using the value D 0 ;
comparing the system-pressure time derivative D(t) to D target until D(t) equals D target ;
determining a target system-pressure p n − where D(t) equals D target ;
calculating the maximum system-pressure S 2 H and the minimum system-pressure S 2 h by means of the target system-pressure p n − and the pre-set system-pressure p 0 − ;
operating the vacuum generator arrangement to reestablish a vacuum system-pressure p − (t) to maximum system-pressure S 2 H when the vacuum system-pressure p − (t) is equal to or closely equal to the minimum system-pressure S 2 h.
2. The method according to claim 1 , wherein the calculation of the value D target is performed by using the equation
D target =k*D 0 ,
wherein 0<k<1.
3. The method according to claim 1 , wherein the calculating step comprises calculating the maximum system-pressure S 2 H by
S 2 H=p 0 − +( p n − −p 0 − )* K 1 ;
and the minimum system-pressure by
S 2 h=p n − −( p n − −S 2 H )* K 2 ;
Where K 1 is set to a value 0.5≤K 1 ≤1.0 and K 2 is set to a value 0≤K 2 ≤20.
4. The method according to claim 1 , wherein the operating step the vacuum generator arrangement is closed (off) if p − (t)>S 2 H and open (on) if p − (t)<S 2 h.
5. The method according to claim 1 , wherein the operating step the vacuum generator arrangement comprises an on/off valve that is closed (off) if p − (t)>S 2 H and open (on) if p − (t)<S 2 h.
6. The method according to claim 1 , wherein system-pressure p − (t) is monitored continuously and fluctuation is detected autonomously.
7. The method according to claim 1 , wherein system-pressure p − (t) is monitored periodically and fluctuation is detected autonomously.
8. A controller for automatic pressure level determination and adaptation enabling energy saving in working cycles in a vacuum system operating a vacuum gripper tool for transportation of objects, said vacuum system comprises a vacuum generator arrangement driven by a compressed air flow, wherein the vacuum generator arrangement via a vacuum chamber being part of the vacuum system is arranged to be brought in flow connection with the vacuum gripper tools, in order to supply vacuum to the vacuum gripper in result of the compressed air flow, wherein a pressure sensor for monitoring a vacuum system-pressure p − (t) is arranged inside the vacuum chamber; and a vacuum system controller being electrically connected to a main controller, wherein the vacuum system controller is arranged to control and communicate with the vacuum generator arrangement and communicate with the pressure sensor, and the vacuum system controller is arranged to monitor the measured system-pressure p − (t) continuously, wherein the vacuum system controller further is capable to calculate a system-pressure time derivative D(t)=dp − /dt during the working cycles, said controller comprising a processor in a processing circuitry being operative to perform the steps of:
determining at start-up of a working cycle value Do of the system-pressure time derivative at a pre-set system-pressure p 0 − ;
calculating value D target of target system-pressure time derivative using the value D 0 ;
comparing the system-pressure time derivative D(t) to D target until D(t) equals D target ;
determining a target system-pressure p n − where D(t) equals D target ;
calculating the maximum system-pressure S 2 H and the minimum system-pressure S 2 h by means of the target system-pressure p n − and the pre-set system-pressure p 0 − ;
operating the vacuum generator arrangement to reestablish a vacuum system-pressure p − (t) to maximum system-pressure S 2 H when the vacuum system-pressure p − (t) is equal to or closely equal to the minimum system-pressure S 2 h.
9. The controller according to claim 8 , wherein the calculation of the value D target is performed by using the equation
D target =k*D 0 ,
wherein 0<k<1.
10. The controller according to claim 8 , wherein the calculation of the maximum system-pressure S 2 H is performed by using the equation
S 2 H=p 0 − +( p n − −p 0 − )* K 1 ;
and the minimum system-pressure (S 2 h ) is performed by using the equation
S 2 h=p n − −( p n − −S 2 H )* K 2 ;
Where K 1 is set to a value 0.5≤K 1 ≤1.0 and K 2 is set to a value 0≤K 2 ≤20.
11. The controller according to claim 8 , wherein the vacuum generator arrangement is operated to close (off) if p − (t)>S 2 H and open (on) if p − (t)<S 2 h.
12. The controller according claim 8 , wherein the vacuum generator arrangement comprises an on/off valve which the vacuum generator arrangement is operated to the vacuum generator arrangement is operated to close (off) if p − (t)>S 2 H and to open (on) if p − (t)<S 2 h.
13. The controller according to claim 8 , wherein system-pressure p − (t) is monitored continuously and fluctuation is detected autonomously.
14. The controller according claim 8 , wherein system-pressure p − (t) is monitored periodically and fluctuation is detected autonomously.