Actuator Speed LASHIP Control using

Transcription

1 ASME/BATH 24 Symposium on Fluid Power & Motion Control September -2, Bath, United Kingdom Actuator Speed LASHIP Control using Laboratory of Digital Hydraulic Hydraulics and Pneumatic Systems Cristiano C. Locateli Henri Carlo Belan Edson R. De Pieri Petter Krus Victor J. De Negri LASHIP Laboratory of Hydraulic and Pneumatic Systems Federal University of Santa Catarina Florianópolis - S.C. Brazil FLUMES - Fluid and Mechatronic Systems Linköping University Linköping, Sweden

2 Introduction C In the last few years, the energetic efficiency of hydraulic systems has been widely discussed... VR VCK VCK2 VD VD2 VD4 VCK4 One approach that has a particular potential is digital hydraulics. P P2 P4 A F A AC AD F L AA AB x A pa pb pc Digital hydraulics has several potential advantages when compared with traditional technology. ps VPA VPB VPC VPD pd V2PA V2PB V2PC V2PD ps2 V3PA V3PB V3PC V3PD Contributions ps3 VAR VBR VCR VDR CPA A A B CPB Return module The main objective of this paper is to discuss the speed control of symmetrical actuators using digital hydraulic principles V4PA V4PB V4R V4AP V2PA V2PB V2R V2AP VPA VAP Suction module Working module VSA VPB VSB VBR M M VR P P2 P4 It is proposed a hydraulic circuit configuration based on use of several fixed displacement and on/off valves. VBS An energy management device is also proposed.

3 Proposal of a Digital Hydraulic System Symmetric actuator C PA A A B C PB Return module V 4PA V 4PB V 4R V 4AP V 2PA V 2PB V 2R V 2AP V PA V PB V R V AP Working module V BR M M P P 2 P 4 Suction module V SA V SB V BS Working module It is responsible for directing the flow rate from the fixed displacement units (FDUs) to the actuator chambers Suction module It allows flow from the actuator chambers to the digital pump Return module It allows the idle operation of the FDUs when they are not providing flow rate to a actuator chamber A preliminary discussion and results, using one symmetrical cylinder, were presented in FPNI PH.D Symposium 24, Finland (Locateli et al., 24)

4 Proposal of a Digital Hydraulic System Two actuators not sharing the same FDUs C PA A A B 2C PA A 2A B C PB Return module Return module 2C PB V 4PA V 4PB V 4R 2V 4R 2V 4PA 2V 4PB 2V 4AP V 4AP V 2PA V 2PB V 2R 2V 2R 2V 2PA 2V 2PB 2V 2AP V 2AP V PA V PB V R 2V R 2V PA 2V PB 2V AP V AP Working module V BR M M P P 2 P 4 2P 4 2P 2 2P 2V BR Working module V SA V SB 2V SA 2V SB Suction module V BS 2V BS Suction module - Independent FDU for each actuator; - Larger number of components; - The actuators can be used simultaneously; - Capacity to reuse energy when moving load applied on the direction of the movement

5 Proposal of a Digital Hydraulic System Two actuators sharing the same FDUs 2C PA A 2A B 2C PB C PA A A B C PB Return module 2V 4PA 2V 4PB V 4PA V 4PB V 4R V 4AP 2V 2PA 2V 2PB V 2PA V 2PB V 2R V 2AP 2V PA 2V PB V PA V PB V R V AP Working module V BR M M P P 2 P 4 Suction module 2V SA 2V SB V SA V SB V BS - Actuators must not use the same FDU at the same time; - Lower number of components; - Reduction in the availability of speed levels for the actuators; - Capacity to reuse energy when moving load applied on the direction of the movement

6 Proposal of a Digital Hydraulic System FDU Operating modes Pump mode When the applied force on the actuator is in the opposite direction of movement Applied force direction Actuator movement direction Motor mode When the applied force on the actuator is in the same direction of movement Applied force direction Actuator movement direction Idle mode When the FDU is in idle condition

7 Control Method The actuator speed is function of which on/off valves are active, prime mover speed and system loads; A B A Seven different speeds; V 4PA V 4PB V 4R The size of digital pump units are defined by mathematical sequence of power of two (, 2 and 4). V 2PA V PA V 2PB V PB V 2R V R Example: Third actuator speed level. The red line represents the FDU operating in pump/motor mode. The blue line represents the flow that leaves chamber B, The green line shows FDU P 4 operating in idle mode V SA V SB V BR M M P P 2 P 4 V BS

8 Control Method The transient state behaviour comprises the transition between speed levels; time between the changes of speed levels; time is applied to minimize hydraulic short circuits; The valve opening time is 4 ms. V PA V 2PA Example: Diagram related to speed changing between the second and third levels. V SB V R V 4R a b c d A control signal is initially sent to close the V R valve of the return module; After a specific delay time, a control signal is sent to open the V PA valve of the working module; During this process, the V 2PA, V SB and V 4R valves remain activated.

9 Operating example Symmetric actuator Transition between the second and third speed levels (slow motion). V PA V 2PA V SB V R V 4R a b c d

10 Results times in the digital hydraulic system % % % 9 9 % Time Time [s] [s] Time Time [s] [s] Time Time [s] [s] Time Time [s] [s] %.2.2 % 2 2 % 2 2 % Actuator speed for four different delay times of the valve input signal

11 Results C PA A A B V 4PA C PB V 4PB Return module V 4R times in the digital hydraulic system V 4AP V 2PA V 2PB V 2R V 2AP V PA V PB V R Flow and control signal on the V 2PA valve V AP Working module V BR M M P P 2 P 4 Suction module V SA V SB V BS Flow rate [l/min] 2 - q V 2PA q V 2R Control signal Flow rate [l/min] 2 of % of 9% - q V 2PA q V 2R Control Signal Flow rate [l/min] -2 u V 2R u V 2PA q V 2PA q V 2R u V 2R u V 2PA of % Control signal Flow rate [l/min] -2 u V 2R q V 2PA q V 2PA q V 2R of 2% -2 u V 2R u V 2PA Control signal

12 Preliminary Results Energy dissipation Energy dissipation with a delay of %. Energy dissipation with a delay of 9 %. Percentage of dissipated energy (%) Total Actuator 4 3 Others 2 V R V SB V PA 936,48 944,59 86,95 58,44 33,3 53,9 Dissipated energy [J] Percentage of total energy (%) Percentage of dissipated energy (%) Total Actuator Others 2 V SB V V 4R BR 57,83 979,4 4,56 92,24 46,85 337,77 Dissipated energy [J] Percentage of total energy (%) The total energy dissipated is nearly 25% of the total energy used by the system. The main dissipation occurs in the V R, V SB and V PA valves The total energy dissipated is nearly 2% of the total energy used by the system. The main valve dissipations occur on the V SB, V 4R, and V BR

13 Preliminary Results Speed control in an open loop Speed response of the symmetrical actuator for step inputs Actuator speed from fifth level on advance movement to third level on retreat A B The higher speed oscillations, both in advance and return movements, take place between the third and fourth levels. The accumulator smooths the changes in the actuator speed, despite of causing a delay in the response. Short time interval of 5 ms.

14 Preliminary Results Speed control in an open loop Pressures in the fixed displacement units for a variation of actuator speed from the fifth level of advance to the third level of retreat 6 p P p P 2 6 p P 2 p P p P 4 p P Pressure [bar] 8 Pressure [bar] 8 Pressure [bar] FDU (P ) From pump mode to motor mode FDU 2 (P 2 ) From idle mode to motor mode FDU 4 (P 4 ) From pump mode To idle mode

15 Proposal of an energy management device Operational modes Red line indicates high pressure Blue line indicates low pressure Arrows show the flow direction V AAr V AAr V AAr C Ar C Ar C Ar V BAr V BAr V BAr V ArR V ArR V ArR V ArP V ArP V ArP P Ar P Ar P Ar V BAr V BAr V BAr Motor mode Idle mode Pump mode - Tends to reduce the energy consumed by the prime mover; - It can be used when the DHS operates in pump mode. - It can be used when the DHS operates in pump mode or idle mode. - It is able to store energy; - It can be used when the DHS operates in motor mode.

16 Proposal of an energy management device Digital hydraulic system with an energy management device C PA A C PB C Ar V AAr V 4PA V 4PB V 4R V 4AP V 2PA V 2PB V 2R V ArR V 2AP V PA V PB V R V AP V BR M M P P 2 P Ar V ArP V SA V SB V BAr V BS - The control action acts on the variation of the volumetric displacement of the VDU and on the states of the V ArR and V ArP valves. - Challenge: Achieving an effective energy management is related to the control strategy.

17 Advantages, Disadvantages, and Challenges of the proposed digital hydraulic system - The hydraulic system losses, due to flow throttling, are reduced and, thus, the efficiency is increased due to the replacement of the continuous directional control valve sor flow control valves by on/off valves; - Possibility to reuse or store the energy when any FDU operates in motor mode due to the use of a closed circuit; - The use of on/off valves in the hydraulic system guarantees a smaller contaminant influence and greater robustness. However, the use of a large number of valves can present problems related to the system physical size and synchronization.

18 Conclusions - This paper has discussed a concept of a hydraulic system that aims to increase energy efficiency using hybrid hydraulic principles; - Preliminary results show the importance of a apropriated control strategy for the opening and closing the on/off valves. A suitable choice enables low actuator speed oscillations and low energy dissipation; - The energy management device enables to store energy in the motor mode reducing the spend energy by the prime motor when the digital hydraulic system operates in pump mode. Ongoing activities by the research groups: Energy management device Digital Actuator Digital Pump V AAr A F A Jet C Ar AA AB AC AD F L x A pa pb pc V BAr VPA VPB VPC VPD pd EM Jet V ArR ps V2PA V2PB V2PC V2PD V ArP ps2 EM Jet P Ar V3PA V3PB V3PC V3PD ps3 V BAr VAR VBR VCR VDR

19 ASME/BATH 24 Symposium on Fluid Power & Motion Control September -2, Bath, United Kingdom Actuator Speed LASHIP Control using Laboratory of Digital Hydraulic Hydraulics and Pneumatic Systems Cristiano C. Locateli Victor J. De Negri Petter Krus