Hi, with commit ca81537edc33c128af3dbfb820b9039aac42e00f I obtained the results below. The slight differences between the implementations could perhaps be avoided with different solver settings. It seems that the corrected implementation also resolves this issue: https://groups.google.com/g/projectchrono/c/m2tswtNze2Q
Thank you very much! Simon *Output using ChLinkMotorRotationSpeed:* ... Time: 0.950 *** Body Angle: 0.950 *** Force Angle: 0.940 *** Torque Angle: -0.631 *** Angle Difference: 1.571 Time: 0.960 *** Body Angle: 0.960 *** Force Angle: 0.950 *** Torque Angle: -0.621 *** Angle Difference: 1.571 Time: 0.970 *** Body Angle: 0.970 *** Force Angle: 0.960 *** Torque Angle: -0.611 *** Angle Difference: 1.571 Time: 0.980 *** Body Angle: 0.980 *** Force Angle: 0.970 *** Torque Angle: -0.601 *** Angle Difference: 1.571 Time: 0.990 *** Body Angle: 0.990 *** Force Angle: 0.980 *** Torque Angle: -0.591 *** Angle Difference: 1.571 *Output using ChLinkLockLock:* ... Time: 0.950 *** Body Angle: 0.950 *** Force Angle: 0.940 *** Torque Angle: -0.621 *** Angle Difference: 1.561 Time: 0.960 *** Body Angle: 0.960 *** Force Angle: 0.950 *** Torque Angle: -0.611 *** Angle Difference: 1.561 Time: 0.970 *** Body Angle: 0.970 *** Force Angle: 0.960 *** Torque Angle: -0.601 *** Angle Difference: 1.561 Time: 0.980 *** Body Angle: 0.980 *** Force Angle: 0.970 *** Torque Angle: -0.591 *** Angle Difference: 1.561 Time: 0.990 *** Body Angle: 0.990 *** Force Angle: 0.980 *** Torque Angle: -0.581 *** Angle Difference: 1.561 On Monday, May 1, 2023 at 8:14:18 PM UTC+2 [email protected] wrote: > Dear users, > > The explanation for the bug and the previous commit ([fb7d16c], on 27th > April) are wrong. The bug of ChLinkLockLock() is not related to the > projection matrix P. > > Today I pushed another commit to fix the bug: > Commit: ca81537edc33c128af3dbfb820b9039aac42e00f [ca81537] > > The reaction torque is simply computed as Cqw2.T*lambda which is expressed > in the local frame of Body2, then it is rotated back to the master frame > (marker2, or frame2, F2) of the joint by left-multiplying R_F2_B2.T. > > Best regards, > Chao PENG. > > 在2023年4月27日星期四 UTC+2 11:00:26<chao peng> 写道： > >> Hello Simon, >> >> Thank you for your test and feedback. I didn't realize there is a same >> bug as in ChLinkMateGeneric(). >> When we use quaternion to parameterize the finite rotation and derive the >> constraint equation (C) and its Jacobian matrix (Cq), we will have a >> projection matrix P to convert the Lagrange multiplier (only for rotational >> DOFs) to the reaction torque. This projection matrix P = >> 0.5(s*I33+\tilde(v)) where \pho_{F1_F2}=(s,v) is the quaternion of the >> slave frame F1 to master frame F2. When F1, F2 are coincident, P=0.5*I33, >> thus we can find a coefficient 0.5 in the code to convert Lagrange >> multipler to reaction torque. But in case there is a relative rotation >> between F1 and F2, the projection matrix P changes, and the Lagrange >> multiplier is expressed in an obscure ghost frame FX (let's denote it as FX >> here). The rotation of FX is a half of the relative rotation in >> \pho_{F1_F2}. Besides this point, it also includes a component which scales >> the Lagrange multiplier by the scalar part 's'. This is why you obtain the >> above result in you test. >> >> We fixed this bug in below commit: >> Commit: fb7d16caa653d837c9220cf96db5aebeb2df8231 [fb7d16c], on 27th April. >> >> Try to pull it and test again. >> >> I would like to remind here, the tangent stiffness matrix (Kc) of >> ChLinkLockLock() is not implemented, although the analytical expression >> should be same as ChLinkMateGeneric(), or at least quite similar. Thus you >> cannot perform the static and eigenvalue analysis for a pendulum using >> ChLinkLockLock(). >> >> Best regards, >> Chao PENG. >> >> 在2023年4月26日星期三 UTC+2 15:32:03<Simon> 写道： >> >>> Hi, >>> >>> thank you for the updated implementation. I re-ran my test case with >>> chrono at commit 841781d6e0e4b09c68cd431e1f7381b402f17ad1. >>> >>> The reaction torque vector does now rotate as expected with >>> ChLinkMotorRotationSpeed. As shown in my example below there is now a >>> constant angle difference of 90° between force and torque in the x-y plane. >>> >>> However, with the ChLinkLockLock implementation I noticed that the angle >>> of the torque vector seems to change only at half the speed of the body >>> rotation. This leads to a constantly changing difference between force and >>> torque direction in the x-y plane. >>> So perhaps there is also something wrong with the ChLinkLockLock's >>> reaction torque direction (see example with output below). >>> >>> Sorry for being naggy, your support is highly appreciated! >>> >>> Best regards, >>> Simon >>> >>> >>> *Code:* >>> ChSystemNSC system{}; >>> >>> auto fixed_body{chrono_types::make_shared<ChBody>()}; >>> fixed_body->SetBodyFixed(true); >>> auto rotating_body{chrono_types::make_shared<ChBody>()}; >>> rotating_body->SetPos({1.0, 0.0, 0.0}); >>> >>> // Option 1: ChLinkMotorRotationSpeed >>> >>> auto >>> rotation_link{chrono_types::make_shared<ChLinkMotorRotationSpeed>()}; >>> rotation_link->Initialize(rotating_body, fixed_body, ChFrame{}); >>> >>> rotation_link->SetSpeedFunction(chrono_types::make_shared<ChFunction_Const>(1.0)); >>> >>> >>> // Option 2: ChLinkLockLock >>> // auto >>> rotation_link{chrono_types::make_shared<ChLinkLockLock>()}; >>> // rotation_link->Initialize(rotating_body, fixed_body, {}); >>> // rotation_link->Set_angleset(chrono::AngleSet::ANGLE_AXIS); >>> // rotation_link->SetMotion_axis({0.0, 0.0, 1.0}); >>> // >>> >>> rotation_link->SetMotion_ang(chrono_types::make_shared<ChFunction_Ramp>(0.0, >>> >>> 1.0)); >>> >>> >>> system.Add(fixed_body); >>> system.Add(rotating_body); >>> system.Add(rotation_link); >>> >>> system.Set_G_acc({0.0, 0.0, 10.0}); >>> >>> for (double time{}; time < 1.0; time += 0.01) >>> { >>> system.DoFrameDynamics(time); >>> >>> const auto body_position{rotating_body->GetPos()}; >>> const double body_angle{std::atan2(body_position[1], >>> body_position[0])}; >>> >>> const auto reaction_force{rotation_link->Get_react_force()}; >>> const double force_angle{std::atan2(reaction_force[1], >>> reaction_force[0])}; >>> >>> const auto reaction_torque{rotation_link->Get_react_torque()}; >>> const double torque_angle{std::atan2(reaction_torque[1], >>> reaction_torque[0])}; >>> >>> >>> std::cout << std::fixed << std::setprecision(3) << "Time: " << >>> system.GetChTime() >>> << " *** Body Angle: " << body_angle << " *** Force Angle: >>> " << force_angle >>> << " *** Torque Angle: " << torque_angle >>> << " *** Angle Difference: " << force_angle - torque_angle >>> << "\n"; >>> } >>> >>> *Output using ChLinkMotorRotationSpeed:* >>> ... >>> Time: 0.950 *** Body Angle: 0.950 *** Force Angle: 0.940 *** Torque >>> Angle: -0.631 *** Angle Difference: 1.571 >>> Time: 0.960 *** Body Angle: 0.960 *** Force Angle: 0.950 *** Torque >>> Angle: -0.621 *** Angle Difference: 1.571 >>> Time: 0.970 *** Body Angle: 0.970 *** Force Angle: 0.960 *** Torque >>> Angle: -0.611 *** Angle Difference: 1.571 >>> Time: 0.980 *** Body Angle: 0.980 *** Force Angle: 0.970 *** Torque >>> Angle: -0.601 *** Angle Difference: 1.571 >>> Time: 0.990 *** Body Angle: 0.990 *** Force Angle: 0.980 *** Torque >>> Angle: -0.591 *** Angle Difference: 1.571 >>> >>> >>> *Output using ChLinkLockLock:* >>> ... >>> Time: 0.950 *** Body Angle: 0.950 *** Force Angle: 0.940 *** Torque >>> Angle: -1.096 *** Angle Difference: 2.036 >>> Time: 0.960 *** Body Angle: 0.960 *** Force Angle: 0.950 *** Torque >>> Angle: -1.091 *** Angle Difference: 2.041 >>> Time: 0.970 *** Body Angle: 0.970 *** Force Angle: 0.960 *** Torque >>> Angle: -1.086 *** Angle Difference: 2.046 >>> Time: 0.980 *** Body Angle: 0.980 *** Force Angle: 0.970 *** Torque >>> Angle: -1.081 *** Angle Difference: 2.051 >>> Time: 0.990 *** Body Angle: 0.990 *** Force Angle: 0.980 *** Torque >>> Angle: -1.076 *** Angle Difference: 2.056 >>> On Monday, April 17, 2023 at 4:48:39 PM UTC+2 [email protected] wrote: >>> >>>> Dear everyone, >>>> >>>> We corrected the bugs reported here. >>>> >>>> Please refer to the commit [d7193ef] on 17th April. >>>> >>>> Welcome to feedback your test result. >>>> >>>> 在2023年3月13日星期一 UTC+1 09:14:49<Simon> 写道： >>>> >>>>> Hi Luning, >>>>> >>>>> thanks for your reply. I agree on the cause of the force and torque >>>>> components, but to my understanding the constant torque vector >>>>> [0.000, -10.000, -0.000] would be correct only in the rotating frame, >>>>> not in the link frame (which is fixed here). >>>>> >>>>> I modified my example, now using ChLinkLockLock to create the same >>>>> rotating body setup (see below). The torque vector seems to rotate >>>>> correctly when using ChLinkLockLock, in contrast to the >>>>> ChLinkMotorRotationSpeed case. >>>>> >>>>> Thank you, >>>>> Simon >>>>> >>>>> *Code:* >>>>> ChSystemNSC system{}; >>>>> >>>>> auto fixed_body{chrono_types::make_shared<ChBody>()}; >>>>> fixed_body->SetBodyFixed(true); >>>>> auto rotating_body{chrono_types::make_shared<ChBody>()}; >>>>> rotating_body->SetPos({1.0, 0.0, 0.0}); >>>>> >>>>> // Option 1: ChLinkMotorRotationSpeed >>>>> // auto >>>>> rotation_link{chrono_types::make_shared<ChLinkMotorRotationSpeed>()}; >>>>> // rotation_link->Initialize(rotating_body, fixed_body, >>>>> ChFrame{}); >>>>> // >>>>> >>>>> rotation_link->SetSpeedFunction(chrono_types::make_shared<ChFunction_Const>(1.0)); >>>>> >>>>> // Option 2: ChLinkLockLock >>>>> auto rotation_link{chrono_types::make_shared<ChLinkLockLock>()}; >>>>> rotation_link->Initialize(rotating_body, fixed_body, {}); >>>>> rotation_link->Set_angleset(chrono::AngleSet::ANGLE_AXIS); >>>>> rotation_link->SetMotion_axis({0.0, 0.0, 1.0}); >>>>> rotation_link->SetMotion_ang(chrono_types::make_shared<ChFunction_Ramp>(0.0, >>>>> >>>>> 1.0)); >>>>> >>>>> >>>>> system.Add(fixed_body); >>>>> system.Add(rotating_body); >>>>> system.Add(rotation_link); >>>>> >>>>> system.Set_G_acc({0.0, 0.0, 10.0}); >>>>> >>>>> for (double time{}; time < 1.0; time += 0.01) >>>>> { >>>>> system.DoFrameDynamics(time); >>>>> >>>>> std::cout << std::fixed << std::setprecision(3) << "Time: " << >>>>> system.GetChTime() >>>>> << " *** Force: " << rotation_link->Get_react_force() >>>>> << " *** Torque: " << rotation_link->Get_react_torque() >>>>> << " *** Link Absolute Coords: " << >>>>> rotation_link->GetLinkAbsoluteCoords() << "\n"; >>>>> } >>>>> >>>>> *Output using ChLinkMotorRotationSpeed:* >>>>> ... >>>>> Time: 0.970 *** Force: 0.574 0.819 10.000 *** Torque: 0.000 -10.000 >>>>> -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 0.000 >>>>> 0.000 >>>>> 0.000 >>>>> Time: 0.980 *** Force: 0.565 0.825 10.000 *** Torque: 0.000 -10.000 >>>>> -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 0.000 >>>>> 0.000 >>>>> 0.000 >>>>> Time: 0.990 *** Force: 0.557 0.831 10.000 *** Torque: 0.000 -10.000 >>>>> -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 0.000 >>>>> 0.000 >>>>> 0.000 >>>>> >>>>> *Output using ChLinkLockLock:* >>>>> ... >>>>> Time: 0.970 *** Force: 0.574 0.819 10.000 *** Torque: 4.662 -8.847 >>>>> -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 0.000 >>>>> 0.000 >>>>> 0.000 >>>>> Time: 0.980 *** Force: 0.565 0.825 10.000 *** Torque: 4.707 -8.824 >>>>> -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 0.000 >>>>> 0.000 >>>>> 0.000 >>>>> Time: 0.990 *** Force: 0.557 0.831 10.000 *** Torque: 4.751 -8.800 >>>>> -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 0.000 >>>>> 0.000 >>>>> 0.000 >>>>> >>>>> On Friday, March 10, 2023 at 6:27:12 PM UTC+1 [email protected] wrote: >>>>> >>>>>> The object is traveling in a circular motion at a constant angular >>>>>> velocity, 1, with respect to the global z coordinate, gravity pointing >>>>>> downward z. Therefore, link force in xy plane is a centrifugal force, F >>>>>> = >>>>>> mw^2R, pointing towards origin, z component balance out gravitational >>>>>> force. With zero angular acceleration, z-component of link torque is >>>>>> zero, >>>>>> y-component balance out the torque from gravity, since rotation around y >>>>>> and z axis are constrained. >>>>>> >>>>>> Thank you, >>>>>> Luning >>>>>> >>>>>> On Friday, March 10, 2023 at 12:10:53 AM UTC-6 Simon wrote: >>>>>> >>>>>>> Hi Luning, >>>>>>> >>>>>>> thanks for the clarification about the link coordinate system. >>>>>>> In my example I added the link coordinate system output to verify >>>>>>> that it is indeed fixed to the global reference frame (see below). >>>>>>> >>>>>>> Unfortunately my question remains: Why does the link force vector >>>>>>> rotate and the torque vector does not ? >>>>>>> >>>>>>> Thank you, >>>>>>> Simon >>>>>>> >>>>>>> >>>>>>> *Code:* >>>>>>> ChSystemNSC system{}; >>>>>>> >>>>>>> auto fixed_body{chrono_types::make_shared<ChBody>()}; >>>>>>> fixed_body->SetBodyFixed(true); >>>>>>> auto rotating_body{chrono_types::make_shared<ChBody>()}; >>>>>>> rotating_body->SetPos({1.0, 0.0, 0.0}); >>>>>>> >>>>>>> auto >>>>>>> rotation_link{chrono_types::make_shared<ChLinkMotorRotationSpeed>()}; >>>>>>> rotation_link->Initialize(rotating_body, fixed_body, ChFrame{}); >>>>>>> >>>>>>> rotation_link->SetSpeedFunction(chrono_types::make_shared<ChFunction_Const>(1.0)); >>>>>>> >>>>>>> system.Add(fixed_body); >>>>>>> system.Add(rotating_body); >>>>>>> system.Add(rotation_link); >>>>>>> >>>>>>> system.Set_G_acc({0.0, 0.0, 10.0}); >>>>>>> >>>>>>> for (double time{}; time < 1.0; time += 0.01) >>>>>>> { >>>>>>> system.DoFrameDynamics(time); >>>>>>> >>>>>>> std::cout << std::fixed << std::setprecision(3) << "Time: " << >>>>>>> system.GetChTime() >>>>>>> << " *** Force: " << rotation_link->Get_react_force() >>>>>>> << " *** Torque: " << rotation_link->Get_react_torque() >>>>>>> << " *** Link Absolute Coords: " << >>>>>>> rotation_link->GetLinkAbsoluteCoords() << "\n"; >>>>>>> } >>>>>>> >>>>>>> >>>>>>> *Output:* >>>>>>> ... >>>>>>> Time: 0.830 *** Force: 0.682 0.731 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.840 *** Force: 0.675 0.738 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.850 *** Force: 0.667 0.745 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.860 *** Force: 0.660 0.751 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.870 *** Force: 0.652 0.758 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.880 *** Force: 0.645 0.764 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.890 *** Force: 0.637 0.771 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.900 *** Force: 0.629 0.777 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.910 *** Force: 0.622 0.783 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.920 *** Force: 0.614 0.790 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.930 *** Force: 0.606 0.796 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.940 *** Force: 0.598 0.802 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.950 *** Force: 0.590 0.808 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.960 *** Force: 0.582 0.813 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.970 *** Force: 0.574 0.819 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.980 *** Force: 0.565 0.825 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> Time: 0.990 *** Force: 0.557 0.831 10.000 *** Torque: 0.000 >>>>>>> -10.000 -0.000 *** Link Absolute Coords: 0.000 0.000 0.000 1.000 >>>>>>> 0.000 0.000 0.000 >>>>>>> >>>>>>> >>>>>>> On Thursday, March 9, 2023 at 4:59:13 PM UTC+1 [email protected] >>>>>>> wrote: >>>>>>> >>>>>>>> Hello Simon, >>>>>>>> >>>>>>>> "As I understand, the link coordinate system is the 'master' body >>>>>>>> system (Body2)." >>>>>>>> This is not correct. Your link coordinate system is defined here, >>>>>>>> >>>>>>>> rotation_link->Initialize(rotating_body, fixed_body, ChFrame{}); >>>>>>>> >>>>>>>> ChFrame{} initialize a reference frame coincide with the global >>>>>>>> reference frame. Because your Body2 (fixed_body) has the same >>>>>>>> orientation >>>>>>>> as the GRF, and it is fixed, it just so happens that your link >>>>>>>> coordinate >>>>>>>> system is the same as the 'master' body system. >>>>>>>> >>>>>>>> You can check the orientation of the link coordinate system using >>>>>>>> this: >>>>>>>> auto quat = rotation_link->GetLinkAbsoluteCoords().rot >>>>>>>> >>>>>>>> Thank you, >>>>>>>> Luning >>>>>>>> >>>>>>>> On Tuesday, March 7, 2023 at 9:45:38 AM UTC-6 Simon wrote: >>>>>>>> >>>>>>>> Hi, >>>>>>>> >>>>>>>> as per the documentation >>>>>>>> <https://api.projectchrono.org/classchrono_1_1_ch_link_motor_rotation_speed.html>, >>>>>>>> >>>>>>>> ChLinkMotorRotationSpeed's member functions Get_react_force() and >>>>>>>> Get_react_torque() return the respective values in link coordinates. >>>>>>>> As I understand, the link coordinate system is the 'master' body >>>>>>>> system (Body2). >>>>>>>> >>>>>>>> In the example below a body rotates around the absolute z axis >>>>>>>> using ChLinkMotorRotationSpeed (the 'master' body is fixed here). As >>>>>>>> expected, the link reaction force consists of a the constant body >>>>>>>> weight in >>>>>>>> z direction and the rotating centrifugal load in the x-y plane. >>>>>>>> However, >>>>>>>> the reaction torque (due to gravity) is constant despite the link's >>>>>>>> rotation. Shouldn't the torque vector also rotate or do I >>>>>>>> misunderstand >>>>>>>> something? >>>>>>>> >>>>>>>> Thanks in advance! >>>>>>>> Simon >>>>>>>> >>>>>>>> >>>>>>>> *Code: * >>>>>>>> ChSystemNSC system{}; >>>>>>>> >>>>>>>> auto fixed_body{chrono_types::make_shared<ChBody>()}; >>>>>>>> fixed_body->SetBodyFixed(true); >>>>>>>> auto rotating_body{chrono_types::make_shared<ChBody>()}; >>>>>>>> rotating_body->SetPos({1.0, 0.0, 0.0}); >>>>>>>> >>>>>>>> auto >>>>>>>> rotation_link{chrono_types::make_shared<ChLinkMotorRotationSpeed>()}; >>>>>>>> rotation_link->Initialize(rotating_body, fixed_body, ChFrame{}); >>>>>>>> >>>>>>>> rotation_link->SetSpeedFunction(chrono_types::make_shared<ChFunction_Const>(1.0)); >>>>>>>> >>>>>>>> system.Add(fixed_body); >>>>>>>> system.Add(rotating_body); >>>>>>>> system.Add(rotation_link); >>>>>>>> >>>>>>>> system.Set_G_acc({0.0, 0.0, 10.0}); >>>>>>>> >>>>>>>> for (double time{}; time < 1.0; time += 0.01) >>>>>>>> { >>>>>>>> system.DoFrameDynamics(time); >>>>>>>> >>>>>>>> std::cout << std::fixed << std::setprecision(3) << "Time: " << >>>>>>>> system.GetChTime() >>>>>>>> << " *** Force: " << rotation_link->Get_react_force() >>>>>>>> << " *** Moment: " << >>>>>>>> rotation_link->Get_react_torque() << "\n"; >>>>>>>> } >>>>>>>> >>>>>>>> >>>>>>>> *Output: ...* >>>>>>>> Time: 0.810 *** Force: 0.697 0.717 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.820 *** Force: 0.690 0.724 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.830 *** Force: 0.682 0.731 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.840 *** Force: 0.675 0.738 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.850 *** Force: 0.667 0.745 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.860 *** Force: 0.660 0.751 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.870 *** Force: 0.652 0.758 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.880 *** Force: 0.645 0.764 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.890 *** Force: 0.637 0.771 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.900 *** Force: 0.629 0.777 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.910 *** Force: 0.622 0.783 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.920 *** Force: 0.614 0.790 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.930 *** Force: 0.606 0.796 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.940 *** Force: 0.598 0.802 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.950 *** Force: 0.590 0.808 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.960 *** Force: 0.582 0.813 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.970 *** Force: 0.574 0.819 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.980 *** Force: 0.565 0.825 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> Time: 0.990 *** Force: 0.557 0.831 10.000 *** Moment: 0.000 >>>>>>>> -10.000 -0.000 >>>>>>>> >>>>>>>> -- You received this message because you are subscribed to the Google Groups "ProjectChrono" group. 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