ADAMS转动副摩擦参数设置.doc

GrantHills Studio鹏哥制作（转载）仅供学习交流，非商业用途！Revolute Joint Friction设置一、Revolute Joint ModelJoint reactions (Fa and Fr), bending moment (Tr), and torque preload (Tprfrc) determine the frictional torque in a revolute joint. You can turn off one or more of these force effects using switches SW1 through SW3. The joint reactions (Fa and Fr) （注：图3中FR21和Ff21） are converted into equivalent torques using the respective friction arm (Rn) （注：图3中p） and pin radius (Rp)（注：图3中r）. The joint bending moment (Tr) is converted into an equivalent torque using pin radius (Rp) divided by bending reaction arm (Rb). The frictional torque (Tfrict) is applied along the axis of rotation in the direction that the FRD block computes. 图1 Revolute Joint Model 图2 Block Diagram of Revolute Joint上述是帮助文件中关于转动副中摩擦的描述。这是一个较为复杂的模型，限于水平，这里将不对bending reaction进行讨论。在模型中也将不对其进行设置。图2是ADAMS中如何将各个因素添加在一起，最终构成整个转动副的摩擦扭矩。 图3 轴颈摩擦力的确定图3是常见的转动副轴颈摩擦模型（机械原理孙恒 陈作模 第六版 P91）。详细分析了轴颈摩擦的原理。设受径向载荷G作用下的轴颈1，在驱动力矩Md作用下，在轴承2中等速转动。轴承2对轴颈1的摩擦力Ff21=fv*G，其中fv=（1-0.5pi）f （注：对于配合进门且未经跑合的转动副取较大值，而对于有较大间隙的转动副去较小值）。摩擦力对轴颈的摩擦力矩为Mf=Ff21*r=fv*G*r。根据轴颈1受力平衡可得：G=-FR21，Md=-Mf，故可得：p=fv*r，其中r为转动副半径，红色圆为摩擦圆，p为摩擦圆半径。更为复杂的模型这里不再讨论，如果是做摩擦方面研究的要更加深入的分析两者的不同。对于一般研究应注意对比图1和图3，有助于将我们所学的摩擦概念与ADAMS中使用的摩擦原理相对应。后面将通过ADAMS中的模型仿真来说明这些问题。二、Friction Regime Determination (FRD)下面讲解了ADAMS中的三种摩擦状态：动摩擦、静动摩擦转变、静摩擦。相信如果可以使用ADAMS软件，那么英语水平还是不错的，这里我就不再翻译，原文是对ADAMS的最好解释，大家自己琢磨吧！（注：红色字体是我觉得文中应该重点关注的内容）Three friction regimes are allowed in ADAMS/View:The regime:Means:Dynamic frictionA joint is in dynamic friction if its joint velocity magnitude exceeds 1.5 times the stiction transition velocity. The dynamic coefficient of friction (md) is used in the computation of frictional forces.Transition between dynamic and static frictionIf the joint velocity magnitude is between 1 and 1.5 times the stiction transition velocity, the joint is considered to be transitioning between static and dynamic friction. A STEP function transitions the coefficient of friction between the dynamic (md) and static (ms) coefficients of friction.Static frictionA joint is in static friction when the joint velocity magnitude falls below the stiction transition velocity. The effective coefficient of friction is computed using the joint creep, joint velocity, and static coefficient of friction ( ms ).Revolute Joint Options：详细讲解了各个参数的含义。For the option:Do the following:Mu StaticDefine the coefficient of static friction in the joint. The magnitude of the frictional force is the product of Mu Static and the magnitude of the normal force in the joint, for example:Friction Force Magnitude, F = Nwhere = Mu Static and N = normal forceThe static frictional force acts to oppose the net force or torque along the Degrees of freedom of the joint.The range is 0.Mu DynamicDefine the coefficient of dynamic friction. The magnitude of the frictional force is the product of Mu Dynamic and the magnitude of the normal force in the joint, for example:Friction force magnitude, F = Nwhere = Mu Dynamic and N = normal forceThe dynamic frictional force acts in the opposite direction of the velocity of the joint.The range is 0.Friction ArmDefine the effective moment arm used to compute the axial component of the friction torque. The default is 1.0, and the range is 0.Bending Reaction ArmDefine the effective moment arm use to compute the contribution of the bending moment on the net friction torque in the revolute joint. The default is 1.0, and the range is 0.Pin RadiusDefines the radius of the pin.The default is 1.0, and the range is 0.Stiction Transition VelocityDefine the absolute velocity threshold for the transition from dynamic friction to static friction. If the absolute relative velocity of the joint marker is below the value, then static friction or stiction acts to make the joint stick.The default is 0.1 length units/unit time on the surface of contact in the joint, and the range is 0.Max Stiction DeformationDefine the maximum displacement that can occur in a joint once the frictional force in the joint enters the stiction regime. The slight deformation allows Adams/Solver to easily impose the Coulomb conditions for stiction or static friction, for example:Friction force magnitude 0.Friction Torque PreloadDefine the preload friction torque in the joint, which is usually caused by mechanical interference in the assembly of the joint.The default is 0.0, and the Range is 0.EffectDefine the frictional effects included in the friction model, either Stiction and Sliding, Stiction, or Sliding. Stiction is static-friction effect, while Sliding is dynamic-friction effect. Excluding stiction in simulations that dont require it can greatly improve simulation speed. The default is Stiction and Sliding.Input Forces to FrictionDefine the input forces to the friction model. By default, all user-defined preloads and joint-reaction force and moments are included. You can customize the friction-force model by limiting the input forces you specify. The inputs for a translational joint are: Preload Reaction Force Bending MomentFriction Inactive DuringSpecify whether or not the frictional forces are to be calculated during a Static equilibrium or Quasi-static simulation.The joint velocity determines the instantaneous friction regime for a joint. The following is a block diagram of the friction regimes available in ADAMS/Solver.图4 Block Diagram of Friction Regimes三、ADAMS模型分析模型是一个简单的圆柱体，与地面间添加转动副，并添加摩擦。本文采用柔性加载，只考虑稳态时的情况（时间足够长时），具体的模型参数大家下载模型（）查看，这里就不再一一论述。 图5 ADAMS模型（施加0.12N.m扭矩）图6 ADAMS模型（施加0.121N.m扭矩）当模型确定后，如果驱动力矩小于产生的摩擦阻力矩，那么系统仍保持静止，如果大于则圆柱体加速转动。通过Mf=Ff21*r=fv*G*r进行计算，通过p=fv*r，由于转动副半径和摩擦圆半径已知，可计算出fv，则整个系统匀速运动的驱动力矩为0.12N.m附近，因此本文中加载了0.12N.m和0.1