Merge branch '364-cif-data-based-synthesis-performance-test-models' into 'develop'

#364 CIF data-based synthesis performance test models

See merge request !317

cif/org.eclipse.escet.cif.documentation/asciidoc/developers/lang-modify.asciidoc

@@ -59,7 +59,7 @@ For each change to the CIF language, follow these steps:
 * Update type checker (`org.eclipse.escet.cif.typechecker`).
 ** Add new constraints to the error and problem messages (`ErrMsg.java`).
 ** Verify the implementation by running `chk.bash`.
-* Update example models for changed syntax and constraints (`org.eclipse.escet.cif.examples`).
+* Update example and benchmark models for changed syntax and constraints (`org.eclipse.escet.cif.examples`).
 * Update pretty printer including set of keywords (`org.eclipse.escet.cif.prettyprinter`).
 * Update common methods (`org.eclipse.escet.cif.common`).
 * Update CIF to CIF transformations and other tools.

cif/org.eclipse.escet.cif.documentation/asciidoc/examples.asciidoc

@@ -18,12 +18,12 @@ indexterm:[examples]
 [[examples-chapter-index]]
 == CIF examples
 
-CIF ships with several examples.
+CIF ships with several examples and benchmark models.
 To obtain these examples, follow these steps:
 
 * Start the Eclipse ESCET IDE.
 * Click menu:File[New > Example...].
-* Select _CIF Examples_ and click btn:[Next].
+* Select _CIF Examples_ or _CIF Benchmarks_ and click btn:[Next].
 * Choose the name of the new project that will be created.
 * Choose a location for the new project, on your hard disk.
 If you leave the _Use default location_ option enabled, the new project will be created in workspace directory.

cif/org.eclipse.escet.cif.examples/benchmarks/festo/_source.txt

+//////////////////////////////////////////////////////////////////////////////
+// Copyright (c) 2022 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available
+// under the terms of the MIT License which is available at
+// https://opensource.org/licenses/MIT
+//
+// SPDX-License-Identifier: MIT
+//////////////////////////////////////////////////////////////////////////////
+
+Model source: Ferdie Reijnen, Martijn Goorden, Joanna van de Mortel-Fronczak, Michel Reniers and Jacobus Rooda, 
+"Application of Dependency Structure Matrices and Multilevel Synthesis to a Production Line" In: Proceedings of the IEEE
+Conference on Control Technology and Applications, pages 458-464, 2018, doi: https://doi.org/10.1109/CCTA.2018.8511449.
+
+Model repository: https://github.com/ffhreijnen/CCTAProductionLine.

cif/org.eclipse.escet.cif.examples/benchmarks/festo/all_stations.cif

+//////////////////////////////////////////////////////////////////////////////
+// Copyright (c) 2018, 2022 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available
+// under the terms of the MIT License which is available at
+// https://opensource.org/licenses/MIT
+//
+// SPDX-License-Identifier: MIT
+//////////////////////////////////////////////////////////////////////////////
+
+import "stations12.cif";
+import "stations34.cif";
+import "station5.cif";
+import "station6.cif";
+
+//Testing - Handling combination
+
+// Elevator is only allowed to ascend when it is safe.
+requirement {A_elevator_up.c_on, A_elevator_down.c_off} needs S_transfer_athalfway.On;
+requirement {A_elevator_up.c_on, A_elevator_down.c_off} needs S_reflective.Off;
+
+// Transfer is allowed to move towards droppos when:
+//  - Currently at drop.
+//  - Currently at middle, testing is safe, testing is empty.
+requirement A_transfer2droppos.c_on needs
+    (S_transfer_atpickup.On) or
+    (S_transfer_athalfway.On and S_elevator_down.On and S_capacitive.Off);
+
+// Transfer is allowed to stop move towards droppos when:
+//  - Currently at droppos.
+//  - Currently at middle, testing is unsafe or non empty.
+requirement A_transfer2droppos.c_off needs
+    (S_transfer_atdrop.On) or
+    (S_transfer_athalfway.On and (S_elevator_down.Off or S_capacitive.On));
+
+
+// Buffer - Processing combination
+
+// The separator is only allowed to release a product when the processing station has a free space.
+requirement A_separator.c_off needs S_atinput.Off;
+
+// The separator is only allowed to release a product when the processing station is in a valid position.
+requirement A_separator.c_off needs S_turntable.On;
+
+
+// Processing - Sorting combination
+// Eject can enable when the sorting has sorted the last product.
+requirement A_eject.c_off needs A_conveyer.Off;
+
+// Testing - Buffering combination
+// The air slide can only be enabled when the buffering station is not full.
+requirement A_airslide.c_on needs S_atin.Off;

cif/org.eclipse.escet.cif.examples/benchmarks/festo/definitions.cif

+//////////////////////////////////////////////////////////////////////////////
+// Copyright (c) 2018, 2022 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available
+// under the terms of the MIT License which is available at
+// https://opensource.org/licenses/MIT
+//
+// SPDX-License-Identifier: MIT
+//////////////////////////////////////////////////////////////////////////////
+
+plant def TwoStateSensor(alg bool InitialOn):
+  uncontrollable u_on, u_off;
+  location On:
+    initial InitialOn;
+    marked  InitialOn;
+    edge u_off goto Off;
+  location Off:
+    initial not InitialOn;
+    marked  not InitialOn;
+    edge u_on  goto On;
+end
+
+plant def TwoStateActuator(alg bool InitialOn):
+  controllable c_on, c_off;
+  location On:
+    initial InitialOn;
+    marked  InitialOn;
+    edge c_off goto Off;
+  location Off:
+    initial not InitialOn;
+    marked  not InitialOn;
+    edge c_on  goto On;
+end
+
+plant def TwoStateActuator2(alg bool InitialOn):
+  controllable c_on, c_off;
+  location On:
+    initial InitialOn;
+    marked;
+    edge c_off goto Off;
+  location Off:
+    initial not InitialOn;
+    marked;
+    edge c_on  goto On;
+end
+
+plant def Button():
+  uncontrollable u_push, u_release;
+  location Released:
+    initial; marked;
+    edge u_push goto Pushed;
+  location Pushed:
+    edge u_release goto Released;
+end

cif/org.eclipse.escet.cif.examples/benchmarks/festo/station5.cif

+//////////////////////////////////////////////////////////////////////////////
+// Copyright (c) 2018, 2022 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available
+// under the terms of the MIT License which is available at
+// https://opensource.org/licenses/MIT
+//
+// SPDX-License-Identifier: MIT
+//////////////////////////////////////////////////////////////////////////////
+
+import "definitions.cif";
+
+// PROCESSING
+
+// Plant:
+// Sensors
+S_atinput      : TwoStateSensor(false);
+S_attest       : TwoStateSensor(false);
+S_atdrill      : TwoStateSensor(false);
+S_atexit       : TwoStateSensor(false);
+S_clamp        : TwoStateSensor(false);
+S_test_ok      : TwoStateSensor(false);
+S_drill_up     : TwoStateSensor(true);
+S_drill_down   : TwoStateSensor(false);
+S_turntable    : TwoStateSensor(true);
+S_Pinitialized : TwoStateSensor(false);
+
+// Actuators
+A_drill     : TwoStateActuator(false);
+A_turntable : TwoStateActuator(false);
+A_drilldown : TwoStateActuator(false);
+A_drillup   : TwoStateActuator(true);
+A_clamp     : TwoStateActuator(false);
+A_tester    : TwoStateActuator(false);
+A_eject     : TwoStateActuator(false);
+
+plant PTimer:
+  controllable c_on, c_reset; uncontrollable u_timeout;
+  location Off:
+    initial; marked;
+    edge c_on goto Running;
+  location Running:
+    edge u_timeout goto Timeout;
+    edge c_reset goto Off;
+  location Timeout:
+    edge c_reset goto Off;
+end
+
+// Dynamics
+// Drill dynamics, sensors are mutually exclusive.
+plant S_drill_up.u_on   needs S_drill_down.Off;
+plant S_drill_down.u_on needs S_drill_up.Off;
+
+// Requirements
+// Initialization
+// The actuators can only activate when the station is initialized.
+requirement {A_drill.c_on, A_drill.c_off, A_turntable.c_on, A_turntable.c_off,
+             A_drilldown.c_on, A_drillup.c_off, A_clamp.c_on, A_clamp.c_off,
+             A_tester.c_on, A_tester.c_off, A_eject.c_on, A_eject.c_off, PTimer.c_on, PTimer.c_reset}
+      needs S_Pinitialized.On;
+
+// A timer that makes sure that the turntable is at stand-still for x seconds, such that sensor measurements can be
+// performed.
+requirement PTimer.c_on    needs S_turntable.On;
+requirement PTimer.c_reset needs S_turntable.Off;
+
+// Turn table
+// The turn table is only allowed to enable at a valid positions.
+requirement A_turntable.c_on  needs S_turntable.On;
+requirement A_turntable.c_on needs PTimer.Timeout;
+
+// The turntable actuator can be disabled when the turntable leaves the valid position.
+requirement A_turntable.c_off needs S_turntable.Off;
+
+// The turntable can only rotate when the other actuators are in a safe position.
+requirement A_turntable.c_on  needs S_drill_up.On;
+requirement A_turntable.c_on  needs S_clamp.Off;
+requirement A_turntable.c_on  needs A_eject.Off;
+requirement A_turntable.c_on  needs A_drill.Off;
+requirement A_turntable.c_on  needs A_tester.Off;
+
+// The turntable can only rotate when a new product has entered.
+requirement A_turntable.c_on  needs S_atinput.On;
+
+// Tester
+// The tester is only allowed to enable when the turntable is at standstill.
+requirement A_tester.c_on  needs S_turntable.On;
+requirement A_tester.c_on  needs A_turntable.Off;
+requirement A_tester.c_on  needs PTimer.Timeout;
+
+// The tester is only allowed to enable when there is a product.
+requirement A_tester.c_on  needs S_attest.On;
+
+// The tester can be disabled once the measurement is completed.
+requirement A_tester.c_off needs S_test_ok.On;
+
+// If there is a product at the testing location, it should be processed, before the turntable is activated again.
+requirement Tester:
+  location One:
+    initial; marked;
+    edge A_turntable.c_on;
+    edge A_tester.c_on goto Two;
+  location Two:
+    edge A_tester.c_off goto Three;
+  location Three:
+    edge A_turntable.c_on goto One;
+end
+
+
+// Clamp
+// The clamp is only allowed to enable when the turn table is at standstill.
+requirement A_clamp.c_on  needs S_turntable.On;
+requirement A_clamp.c_on  needs A_turntable.Off;
+requirement A_clamp.c_on  needs PTimer.Timeout;
+
+// The clamp is only allowed to enable when a product is available.
+requirement A_clamp.c_on  needs S_atdrill.On;
+
+// The clamp can only be released when the drill is up.
+requirement A_clamp.c_off needs S_drill_up.On;
+
+// The clamp can only be released when the drill is disabled.
+requirement A_clamp.c_off needs A_drill.Off;
+
+
+// Drill
+// The drill is only allowed to enable at the upper position.
+requirement A_drill.c_on  needs S_drill_up.On;
+
+// The drill is only allowed to activate when there is a clamped product.
+requirement A_drill.c_on  needs S_clamp.On;
+
+// The drill is only allowed to disable at the upper position.
+requirement A_drill.c_off needs S_drill_up.On;
+
+
+// Drill movement
+// The drill is only allowed to descend when it is fully ascended.
+requirement {A_drillup.c_off, A_drilldown.c_on} needs S_drill_up.On;
+
+// The drill is only allowed to ascend  when it is fully descended.
+requirement {A_drillup.c_on, A_drilldown.c_off} needs S_drill_down.On;
+
+// The cycle at the drilling location should be as follows:
+// Clamp product, activate drill, descend, ascend, deactivate drill, release product.
+requirement ClampDrill:
+  location One:
+    initial; marked;
+    edge A_turntable.c_on;
+    edge A_clamp.c_on goto Two;
+  location Two:
+    edge A_drill.c_on goto Three;
+  location Three:
+    edge A_drillup.c_off goto Four;
+  location Four:
+    edge A_drilldown.c_on goto Five;
+  location Five:
+    edge A_drilldown.c_off goto Six;
+  location Six:
+    edge A_drillup.c_on goto seven;
+  location Seven:
+    edge A_drill.c_off goto Eight;
+  location Eight:
+    edge A_clamp.c_off goto Nine;
+  location Nine:
+    edge A_turntable.c_on goto One;
+end
+
+// Eject
+// The ejector are only allowed to enable when the turntable is at stand-still.
+requirement A_eject.c_on needs S_turntable.On;
+requirement A_eject.c_on needs A_turntable.Off;
+requirement A_eject.c_on needs PTimer.Timeout;
+
+// The ejector is only allowed to enable when there is a product.
+requirement A_eject.c_on  needs S_atexit.On;
+
+// The ejector can be retracted if the product is removed.
+requirement A_eject.c_off needs S_atexit.Off;

cif/org.eclipse.escet.cif.examples/benchmarks/festo/station6.cif

+//////////////////////////////////////////////////////////////////////////////
+// Copyright (c) 2018, 2022 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available
+// under the terms of the MIT License which is available at
+// https://opensource.org/licenses/MIT
+//
+// SPDX-License-Identifier: MIT
+//////////////////////////////////////////////////////////////////////////////
+
+import "definitions.cif";
+
+// SORTING
+
+// Plant:
+// Sensors
+S_product      : TwoStateSensor(false);
+S_inductive    : TwoStateSensor(false);
+S_optical      : TwoStateSensor(false);
+S_slidefull    : TwoStateSensor(false);
+S_gate1_opened : TwoStateSensor(true);
+S_gate1_closed : TwoStateSensor(false);
+S_gate2_opened : TwoStateSensor(true);
+S_gate2_closed : TwoStateSensor(false);
+S_Sinitialized : TwoStateSensor(false);
+
+// Actuators
+A_conveyer       : TwoStateActuator(false);
+A_gate1          : TwoStateActuator(false);
+A_gate2          : TwoStateActuator(false);
+A_stopperretract : TwoStateActuator(false);
+
+plant STimer:
+  controllable c_on, c_reset; uncontrollable u_timeout;
+  location Off:
+    initial; marked;
+    edge c_on goto Running;
+  location Running:
+    edge u_timeout goto Timeout;
+    edge c_reset goto Off;
+  location Timeout:
+    edge c_reset goto Off;
+end
+
+// Dynamics
+// Gate1 dynamics, sensors are mutually exclusive.
+plant S_gate1_opened.u_on needs S_gate1_closed.Off;
+plant S_gate1_closed.u_on needs S_gate1_opened.Off;
+
+// Gate2 dynamics, sensors are mutually exclusive.
+plant S_gate2_opened.u_on needs S_gate2_closed.Off;
+plant S_gate2_closed.u_on needs S_gate2_opened.Off;
+
+// Requirements
+// Initialization
+// Actuators are only allowed to enable/disable when the station is initialized.
+requirement {A_conveyer.c_on, A_conveyer.c_off, A_gate1.c_on, A_gate1.c_off,
+             A_gate2.c_on, A_gate2.c_off, A_stopperretract.c_on, A_stopperretract.c_off}
+      needs S_Sinitialized.On;
+
+// Timer that time out after x seconds, to make sure that a product is identified.
+requirement STimer.c_on    needs S_product.On;
+requirement STimer.c_reset needs S_slidefull.On;
+
+// Conveyer
+// Conveyer is allowed to enable when there is a product.
+requirement A_conveyer.c_on  needs S_product.On;
+
+// Conveyer is allowed to disable when product is in the slide.
+requirement A_conveyer.c_off needs S_slidefull.On;
+
+
+// Stopper
+// Stopper is allowed to retract when:
+//   - There is a product that has been identified (Timeout).
+//   - The slide is not full.
+
+requirement A_stopperretract.c_on  needs STimer.Timeout;
+requirement A_stopperretract.c_on  needs S_slidefull.Off;
+
+// Stopper is allowed to extend when the product entered the buffer.
+requirement A_stopperretract.c_off needs S_slidefull.On;
+
+// Gates
+// The gates are only allowed to close when they are fully open.
+requirement A_gate1.c_on needs S_gate1_opened.On;
+requirement A_gate2.c_on needs S_gate2_opened.On;
+
+// The gates are only allowed to open when they are fully closed.
+requirement A_gate1.c_off needs S_gate1_closed.On;
+requirement A_gate2.c_off needs S_gate2_closed.On;
+
+// Gate1 is only allowed to close when there is a plastic product before the stopper.
+requirement A_gate1.c_on needs S_optical.On;
+requirement A_gate1.c_on needs S_inductive.Off;
+requirement A_gate1.c_on needs STimer.Timeout;
+
+// Gate1 is only allowed to open when product entered the buffer.
+requirement A_gate1.c_off needs S_slidefull.On;
+
+// Gate2 is only allowed to close when there is a metal product before the stopper.
+requirement A_gate2.c_on needs S_optical.On;
+requirement A_gate2.c_on needs S_inductive.On;
+requirement A_gate2.c_on needs STimer.Timeout;
+
+// Gate2 is only allowed to open when product entered the buffer.
+requirement A_gate2.c_off needs S_slidefull.On;
+
+// Gate1 and 2 are only allowed to actuate when the stopper is closed.
+requirement {A_gate1.c_on, A_gate1.c_off} needs A_stopperretract.Off;
+requirement {A_gate2.c_on, A_gate2.c_off} needs A_stopperretract.Off;

cif/org.eclipse.escet.cif.examples/benchmarks/festo/stations12.cif

+//////////////////////////////////////////////////////////////////////////////
+// Copyright (c) 2018, 2022 Contributors to the Eclipse Foundation
+//
+// See the NOTICE file(s) distributed with this work for additional
+// information regarding copyright ownership.
+//
+// This program and the accompanying materials are made available
+// under the terms of the MIT License which is available at
+// https://opensource.org/licenses/MIT
+//
+// SPDX-License-Identifier: MIT
+//////////////////////////////////////////////////////////////////////////////
+
+import "definitions.cif";
+
+// DISTRIBUTING
+
+// Plant:
+// Sensors
+S_product1      : TwoStateSensor(false);
+S_product2      : TwoStateSensor(false);
+S_product3      : TwoStateSensor(false);
+S_pusher1_in    : TwoStateSensor(true);
+S_pusher1_out   : TwoStateSensor(false);
+S_stack1_filled : TwoStateSensor(true);
+S_pusher2_in    : TwoStateSensor(true);
+S_pusher2_out   : TwoStateSensor(false);
+S_stack2_filled : TwoStateSensor(true);
+S_pusher3_in    : TwoStateSensor(true);
+S_pusher3_out   : TwoStateSensor(false);
+S_stack3_filled : TwoStateSensor(true);
+S_Dinitialized  : TwoStateSensor(false);
+
+// Actuators
+A_pusher1 : TwoStateActuator(false);
+A_pusher2 : TwoStateActuator(false);
+A_pusher3 : TwoStateActuator(false);
+
+// Dynamics
+plant S_pusher1_in.u_on  needs S_pusher1_out.Off;
+plant S_pusher1_out.u_on needs S_pusher1_in.Off;
+
+plant S_pusher2_in.u_on  needs S_pusher2_out.Off;
+plant S_pusher2_out.u_on needs S_pusher2_in.Off;
+
+plant S_pusher3_in.u_on  needs S_pusher3_out.Off;
+plant S_pusher3_out.u_on needs S_pusher3_in.Off;
+
+// Requirements
+// Actuators are only allowed to actuate when the station is initialized.
+requirement {A_pusher1.c_on, A_pusher1.c_off} needs S_Dinitialized.On;
+requirement {A_pusher2.c_on, A_pusher2.c_off} needs S_Dinitialized.On;
+requirement {A_pusher3.c_on, A_pusher3.c_off} needs S_Dinitialized.On;
+
+// The Pusher is only allowed to move backwards/out when it is completely in.
+requirement A_pusher1.c_on  needs S_pusher1_in.On;
+requirement A_pusher2.c_on  needs S_pusher2_in.On;
+requirement A_pusher3.c_on  needs S_pusher3_in.On;
+
+// The Pusher is only allowed to move forwards/in when it is completely out.
+requirement A_pusher1.c_off needs S_pusher1_out.On;
+requirement A_pusher2.c_off needs S_pusher2_out.On;
+requirement A_pusher3.c_off needs S_pusher3_out.On;
+
+// The Pusher is only allowed to move backwards/out when the product has been removed.
+requirement A_pusher1.c_on  needs S_product1.Off;
+requirement A_pusher2.c_on  needs S_product2.Off;
+requirement A_pusher3.c_on  needs S_product3.Off;
+
+// The Pusher is only allowed to move forwards/in when there is a product in front of it.
+requirement A_pusher1.c_off needs S_stack1_filled.On;
+requirement A_pusher2.c_off needs S_stack2_filled.On;
+requirement A_pusher3.c_off needs S_stack3_filled.On;
+
+// The Pusher is only allowed to move forward when there is no product at the pickup position.
+requirement A_pusher1.c_off needs S_product1.Off;
+requirement A_pusher2.c_off needs S_product2.Off;
+requirement A_pusher3.c_off needs S_product3.Off;
+
+
+// HANDLING
+
+// Plant:
+// Sensors
+S_product4           : TwoStateSensor(false);
+S_xpos_at1           : TwoStateSensor(false);
+S_xpos_at2           : TwoStateSensor(false);
+S_xpos_at3           : TwoStateSensor(false);
+S_xpos_atdrop        : TwoStateSensor(true);
+S_zpos_atup          : TwoStateSensor(true);
+S_zpos_atdown        : TwoStateSensor(false);
+S_gripper            : TwoStateSensor(false);
+S_transfer_atpickup  : TwoStateSensor(false);
+S_transfer_atdrop    : TwoStateSensor(false);
+S_transfer_athalfway : TwoStateSensor(true);
+S_vacuum             : TwoStateSensor(false);
+S_Hinitialized       : TwoStateSensor(false);
+
+// Actuators
+A_x2distributing   : TwoStateActuator(true);
+A_x2testing        : TwoStateActuator(true);
+A_zdown            : TwoStateActuator(false);
+A_gripperclose     : TwoStateActuator(false);
+A_transfer2pickpos : TwoStateActuator2(false);
+A_transfer2droppos : TwoStateActuator2(false);
+A_vacuum           : TwoStateActuator(false);
+A_ejectpulse       : TwoStateActuator(false);
+
+// Dynamics
+// Xpos dynamics, sensors are mutually exclusive.
+plant S_xpos_at1.u_on    needs S_xpos_at2.Off and S_xpos_at3.Off and S_xpos_atdrop.Off;
+plant S_xpos_at2.u_on    needs S_xpos_at1.Off and S_xpos_at3.Off and S_xpos_atdrop.Off;
+plant S_xpos_at3.u_on    needs S_xpos_at1.Off and S_xpos_at2.Off and S_xpos_atdrop.Off;
+plant S_xpos_atdrop.u_on needs S_xpos_at1.Off and S_xpos_at2.Off and S_xpos_at3.Off;
+
+// Zpos dynamics, sensors are mutually exclusive.
+plant S_zpos_atup.u_on   needs S_zpos_atdown.Off;
+plant S_zpos_atdown.u_on needs S_zpos_atup.Off;
+
+// Transfer dynamics, sensors are mutually exclusive.
+plant S_transfer_atpickup.u_on  needs S_transfer_atdrop.Off   and S_transfer_athalfway.Off;
+plant S_transfer_atdrop.u_on    needs S_transfer_atpickup.Off and S_transfer_athalfway.Off;
+plant S_transfer_athalfway.u_on needs S_transfer_atdrop.Off   and S_transfer_atpickup.Off;
+
+// Requirements
+// Actuators are only allowed to enable/disable when the station is initialized.
+requirement {A_x2distributing.c_on, A_x2distributing.c_off, A_x2testing.c_on, A_x2testing.c_off,
+             A_zdown.c_on, A_zdown.c_off, A_gripperclose.c_on, A_gripperclose.c_off,
+             A_transfer2pickpos.c_on, A_transfer2pickpos.c_off, A_transfer2droppos.c_on, A_transfer2droppos.c_off,
+             A_vacuum.c_on, A_vacuum.c_off, A_ejectpulse.c_on, A_ejectpulse.c_off} needs S_Hinitialized.On;
+
+// Gripper Y position:
+
+// The gripper is only allowed to descend when it is fully ascended.
+requirement A_zdown.c_on  needs S_zpos_atup.On;
+
+// The gripper is only allowed to ascend when it is fully descended.
+requirement A_zdown.c_off needs S_zpos_atdown.On;
+
+// The gripper is only allowed to descend when the gripper is at stand-still.
+requirement A_zdown.c_on  needs A_x2distributing.On and A_x2testing.On;
+
+// The gripper is only allowed to descend when:
+//   - Is at station 1 while station 1 is filled, and the gripper is empty
+//   - Is at station 2 while station 2 is filled, and the gripper is empty
+//   - Is at station 3 while station 3 is filled, and the gripper is empty
+//   - Is at station 4 while station 4 is empty,  and the gripper is filled.
+requirement A_zdown.c_on needs
+    (S_xpos_at1.On    and S_product1.On  and S_gripper.Off) or
+    (S_xpos_at2.On    and S_product2.On  and S_gripper.Off) or
+    (S_xpos_at3.On    and S_product3.On  and S_gripper.Off) or
+    (S_xpos_atdrop.On and S_product4.Off and S_gripper.On);
+
+// The gripper is only allowed to ascend when:
+//   - Is at station 1 while the gripper is closed, and a product is detected
+//   - Is at station 2 while the gripper is closed, and a product is detected
+//   - Is at station 3 while the gripper is closed, and a product is detected