About Adjusting Your Model Before SimulationBefore you begin your simulation, you may want to do one or more preliminary operations to help ensure a better simulation. You can do any of the following:• Check to see if you have the expected number of movable parts and the expected number and type of constraints in your model.• Determine the total number of system degrees of freedom (DOF) and which, if any, constraint equations are redundant. Learn more .• Check to see if any constraints are broken or incorrectly defined and, if so, perform an initial conditions simulation on your model to try to correct these broken joints. Learn more .• Perform a static simulation to move your model into an equilibrium configuration immediately before performing a dynamic simulation to reduce some of the initial, transient system response.• Calculate the natural frequencies of your model as linearized about a particular operating configuration. Learn morePerforming Initial Conditions SimulationYou can perform an initial conditions simulation to check for any inconsistencies in your model. The initial conditions simulation is often referred to as an assemble model operation. An initial conditions simulation tries to reconcile any positioninginconsistencies that exist in your model at its design configuration and make it suitable for performing a nonlinear or linear simulation. Most importantly, the initialconditions simulation tries to ensure that all joint connections are defined properly. For example, for a revolute joint to be defined properly, the origins of the markers that define the joint must be coincident throughout a simulation. If the markers are not coincident, the joint is broken and needs to be repaired. In this example, the initial conditions simulation helps repair the broken revolute joint by moving the origins of the two markers until they are coincident, as shown in the following figure.Consistent Gears that Become InconsistentIn the case of the door with two hinges, Adams/Solver ignores five of the constraint equations that it finds redundant. You do not know which equations Adams/Solver ignores, however. If Adams/Solver ignores all of the equations corresponding to one of the hinges, then all the reaction forces are concentrated at the other hinge in the Adams/Solver solution. Adams/Solver arbitrarily sets the reaction forces to zero at the redundant hinge. But Adams/Solver might not discard all the equations for one hinge and retain all the equations from the other. It might just as easily retain one or more equations from each, and discard one or more from each.Although Adams/Solver still provides the physically correct solution, the simulation may require extra computational effort to constrain the motion when all of the constraint forces and torques are concentrated at one end of the door. Consequently, it is always a good idea to carefully select your constraints and define models without any redundancies. For example, you can construct the model of the door with a spherical joint and a parallel-axes constraint instead of the single revolute joint.Door Frame with Spherical and Parallel-axes ConstraintsWhen you verify your model or run a simulation, Adams/Solver tells you which constraints are redundant. To solve the redundancy, try replacing a redundant idealized joint with a joint primitive. You may also want to replace redundant constraints with approximately equivalent flexible connections.Adams/Solver does not always check the initial conditions set for a constraint when it performs overconstraint checking. If you apply a motion on one joint and initial conditions on another joint, check to ensure that they are not redundant because Adams/Solver does not check them for redundancy and your model may lock up when simulation begins. As a general rule, do not specify more initial conditions than the number of DOF in your model. For more on initial conditions for joints, see Setting Initial Conditions.Examples of Redundant Constraint MessagesThe following sections provide examples of redundant constraint messages and ways to avoid the redundancies:• Example 1 - Converting a Revolute to a Spherical• Example 2 - Converting a Translation to an Inline• Example 3 - Removing Redundancies from Fourbar MechanismExample 1 - Converting a Revolute to a SphericalIf in your model, Joint_7 is a revolute joint, and Adams/View gives you the following warning messages, then you have two redundant constraint equations:Joint_7 unnecessarily removes Rotation Between Zi and XjJoint_7 unnecessarily removes Rotation Between Zi and YjThese messages indicate that the rotational constraint equations 4 and 5 that the revolute joint introduces are not needed. Therefore, you could replace the revolute joint with a spherical joint since it does not use these equations.Example 2 - Converting a Translation to an InlineIf in your model, Joint_29 is a translational joint, and Adams/View displays the following warning messages, then you could change Joint_29 from a translational joint to an inline joint to remove the redundancies:Joint_29 unnecessarily removes Rotation Between Zi and XjJoint_29 unnecessarily removes Rotation Between Zi and YjJoint_29 unnecessarily removes Rotation Between Xi and YjExample 3 - Removing Redundancies from Fourbar MechanismIf you build a fourbar mechanism with four revolute joints, Adams/View displays messages similar to the following:Joint_1 unnecessarily removes Rotation Between Zi and XjJoint_1 unnecessarily removes Rotation Between Zi and YjJoint_3 unnecessarily removes Rotation Between Zi and XjThese messages indicate that you could change Joint_1 from a revolute joint to a spherical joint, and change Joint_3 from a revolute joint to a universal or Hooke joint. By changing the joint types, you eliminate the redundant constraint warnings and possibly improve the performance of your solution.Alternatively, you could also remove the redundancies by changing just one of the revolute joints to an inline joint. There is almost always more than one way to remove redundant constraints. The best way is to select joint types so they match the way your physical system can move. Some of the possible configurations are shown in the figure below.Alternative Configurations for Fourbar MechanismRemember that Adams/Solver does not calculate joint reaction forces in any directions associated with redundant constraint equations because it automatically removes these equations when it performs a simulation. Therefore, you may also want to select your joint types based on where you want to measure joint reaction forces.Performing Static Equilibrium SimulationsWhen you perform a static equilibrium simulation on your model, Adams/Solver iteratively repositions all parts in an attempt to balance all the forces for one particular point in time.To learn more:• About Performing Static Equilibrium Simulations• Finding Static Equilibrium for Your Model• About Performing Dynamic Simulations to Find Static EquilibriumPerforming Initial Conditions SimulationYou can perform an initial conditions simulation to check for any inconsistencies in your model. The initial conditions simulation is often referred to as an assemble model operation. An initial conditions simulation tries to reconcile any positioning inconsistencies that exist in your model at its design configuration and make it suitable for performing a nonlinear or linear simulation. Most importantly, the initial conditions simulation tries to ensure that all joint connections are defined properly. For example, for a revolute joint to be defined properly, the origins of the markers that define the joint must be coincident throughout a simulation. If the markers are not coincident, the joint is broken and needs to be repaired. In this example, the initial conditions simulation helps repair the broken revolute joint by moving the origins of the two markers until they are coincident, as shown in the following figure.Repaired Revolute JointYou can also use the initial conditions simulation if you are creating parts in exploded view. Exploded view is simply creating the individual parts separately and then assembling them together into a model. You might find this convenient if you have several complicated parts that you want to create individually without seeing how they work together until much later. Adams/View provides options for specifying that you are creating your model in exploded view as you create constraints.To perform an initial conditions simulation:• From the Simulation Controls dialog box, select the Initial Conditions tool. Adams/View tells you when it has assembled your model properly. You can revert back to your original design configuration or you can save your assembled model as the new design configuration for your model. For more information on how to do this, see Saving a Simulation Frame.相关主题PopupPopup另请参阅Popup（注：可编辑下载，若有不当之处，请指正，谢谢!）。
