simpack 系统动力学.pdf

Multi body System Dynamics 方向华 总监 GET集团北京分公司 Model Setup in SIMPACK BodiesJointsForce Elements ConstraintsExcitationsSensors Mass Center of I Tensor Marker 3D Primitive from Marker to Marker Type from Marker to Marker Type from Marker to Marker Type Type Paramete r u Vectors from Marker to Marker Type Draw Topology Separate into Bodies Joints Force Elements FEMCAD External Data Real System 物理系统抽象物理系统抽象 Open MBS Tree StructureClosed Loop MBS Tree Structure 开环 闭环拓扑结构开环 闭环拓扑结构 Inertial Frame Joint 1 1 DOF Joint 2 Joint 3 Body 1 Body 2 One of the possible Solutions in SIMPACK relative Kinematics Joints 1 2 define the Topology in SIMPACK joints Joint 3 defines closed Loop in SIMPACK constraints joints give system degrees of freedom constraints lock motion close kinematic chains make closed loops reduce number of degrees of freedom Z Y X Application Example Simple Crank 正弦机构正弦机构 Joints Constraints x y z 1313 Body name Reference Frame Constraint Bodies Joints Force Elements with name of body with from Marker to Marker locked direction of motion in Coordinates of from Marker with from Marker to Marker joint state position in Coordinates of from Marker with SIMPACK force element type cmp calculated w r t from Marker Isys DOFsystem FOSsystem joint 1 DOF Revolution around x Axis Body 2 joint 1 DOF Revolution around x Axis constraint L z locked Transl in z reduce Number of DOF Body 1 Task How do you calculate the Number of Degrees of Freedom DOF of closed Loop Systems and Number of first order States FOS Z Y X 正弦机构正弦机构 Task How do you calculate the Number of Degrees of Freedom of closed Loop Systems DOF and Number of first order States FOS DOFsystem DOFjoint constraint FOSsystem 2 DOFjoint constraint joint 1 DOF Revolution around x Axis Body 2 joint 1 DOF Revolution around x Axis constraint L z locked Transl in z reduce Number of DOF Body 1 Number of differential Equations Number of algebraic Equations Z Y X 正弦机构正弦机构 DOF system DOFsystem DOFjoint constraint FOS system FOSsystem 2 DOFjoint constraint Joint 4 Joint 3 Joint 2 Joint 1 Body 3 Body 2 Body 1 Body 3 Body 2Body 1 L y z Solution 1 Solution 2 DOFsystem 18 17 1 FOSsystem 36 17 53 DOFsystem 3 2 1 FOSsystem 6 2 8 Body 3 Body 2 Body 1 6 DOF 6 DOF L x y z 6 DOF L x y z L y z L x y z Z Y X Smart SIMPACK Model Stupid SIMPACK Model Independent and Dependent Joints N Independent Joints DOFjoint N Joint States constraint DOFsystem Solution II dep indep Solution I indep dep non linear implicit equations solved by Newton Iteration solution depending on initial joint states of body a and b Problem a b indep Multiple Solutions are possible dep Z Y X Isys x y Draw Topologie of McPherson Suspension System DOFsystem DOFjoint constraint FOSsystem 2 DOFjoint constraint Isys x y body Reference Frame Constraints Bodies Joints Force Elements dummy wheel platearm steering rod damper upperdamper lower wheel rackdummy 0DOF Draw Topologie of McPherson Suspension System body Reference Frame Constraints Bodies Joints Force Elements Isys x y 0 DOF 0DOF dummy wheel platearm steering rod damper upperdamper lower x y z x y z z spring damper help tyre wheel DOFsystem DOFjoint constraint 8 6 2 FOSsystem 2 DOFjoint constraint 18 6 24 rackdummy Exercise 4 2 Set Up of a Complex Complete Vehicle Model track joint 19 vehicle reference system Topologie Automotive Plus Models before definition of Substruktur Intersections e g Substructures Steering and Front Axle Left 6 DOF Type 19 Sub STEER dummy 0 DOF Sub FRONT AXLE LEFT dummy chassis 0 DOF dummy steering 0 DOF Exercise 4 3 Set Up of a Complex Complete Vehicle Model track joint 19 vehicle reference system Topologie Automotive Plus Models after definition of Substruktur Intersections e g Substructures Steering and Front Axle Left 6 DOF Type 19 Sub STEER dummy 0 DOF Sub FRONT AXLE LEFT dummy chassis 0 DOF dummy steering 0 DOF Exercise 4 4 Set Up of a Complex Complete Vehicle Model Sub REAR AXLE RIGHT tyre fl 49 Topologie Automotive Plus Models e g Simple Complete Car 6 DOF Type 19 Sub STEER dummy 0 DOF 0 DOF track joint 19 vehicle reference system Sub REAR AXLE LEFT dummy chassis Sub FRONT AXLE RIGHT dummy chassis dummy steering 0 DOF 0 DOF Sub FRONT AXLE LEFT dummy chassis dummy steering 0 DOF 0 DOF dummy chassis tyre rl 49 tyre rr 49 tyre fr 49 The model consists of the following functional bodies ENG engine block CRS crankshaft CNR conrod 4x PIN pin 4x PIS piston 4x TSP torsional damper primary TSS torsional damper secondary FLP flywheel primary FLS flywheel secondary CLU clutch LOD engine load brake x z y Draw Topology of the Complete Model and Check DOF and FOS DOFsystem DOFjoint constraint FOSsystem 2 DOFjoint constraint CHA CRS CNR PIN PIS FLPFLSTSSCLU ENG LOD TSP body Reference Frame Constraints Bodies Joints Force Elements Connector Body 0 DOF Connector Model Substructure The engine model should consist out of four substructures Engine block with crankshaft to be created Crank train with gas forces to be created Additional masses flywheel clutch torsional damper predefined Engine load brake torque predefined Create substructure engine block with crankshaft Review topology of the substructure Review DOFs of the substructure ENG Connector DOF 0DOF 6 CRS FEL 43 4x 716DOF ENG Create substructure crank train CNR CRS Connector DOF 0 PIN 022DOF CTR ENG Connector DOF 0 PIS y DOF 0 FEL 50 Gas force 0 DOF 6 DOF Assemble the main model 1 CHA FE 43 4x CNR PINFE 50 PIS CTR 4x FLPFLS 0 DOF TSS 0 DOF 0 DOF CLU 0 DOF y 0 DOF d d d ADM ADM LOD Excitation u t 0 DOF TSP ENB 01 CRB 01 FE 13 LOD 724247DOF GAS CRS ENG d d d Every body in the MBS model has it s own BFRF The BFRF is always located at 0 0 0 by definition and can not be deleted All body fixed marker coordinates are given with respect to the BFRF except marker coordianates given relatively to a reference marker Even if the BFRF is an ordinary marker it is not recommended to use it for modelling purposes In order to keep a clear model structure it is better to create a new marker at 0 0 0 and assign an appropriate name to it 0 0 0 BFRF P1BFRF P2BFRF P1 P2 The position of a body in space is given by its relation to the inertia system Isys or another body Example Body1 is fixed to the inertia system with its BFRF at P1 Body2 is rotating around P3 on Body1 The position of a body in space results from the joint definition of this body assignment of joint coupling markers 1 1 1 1Isys 1Body1 z y x BFRF BFRF 0 0 0 0 0 0 22BFRFBody 23BodyBFRFP 24BodyBFRFP 12BodyBFRFP 13BodyBFRFP Isys IsysIsysP1 Graphical elements 3D primitives are visualisation elements without any physical meaning except functional primitves like e g gearwheels to the MBS system The position of any 3D primitive on a body is given with respect to a marker located on the body most commonly the BFRF P1 belongs to Body1 even if no 3D graphic is visible at it s location The cuboid is defined with respect to BFRF with primitve built in coordinates of P2 The center of the sphere is defined with respect to P2 with additional primitve built in coordinates Therefore no marker is needed in it s center Isys center center center sphereP2 z y x r r center center center cuboidBFRF z y x r r P2 BFRF P1 Changing the built in positions of 3D primitives will not change the position of the body in space Even if the shape of the body has changed all marker positions will stay at the same location The body did not move at all Isys center center center sphereP2 z y x r r center center center cuboidBFRF z y x r r P2 BFRF P1 Marker coordinates from an assembly drawing only SIMPACK body coordinates given in the Assembly Coordinate System Isys BFRF e g Vehicle coordinate system Example 1 body joint definition at position P2 between marker P2 in Isys and marker P2 on body BFRFIsys P2 P2 P2 IsysBFRF z y x P2P2 P2 P1 CG CG CG CG IsysBFRF z y x CGCG P1 P1 P1 IsysBFRF z y x P1P1 Example 2 body joint definition at position P2 between marker P2 in Isys and marker P2 on body Marker coor