Problem in the torque output of Joint Sensor in SimMechanics
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From: Hiba on 2 Jun 2010 04:55 hello, I have a problem in the values of torque at the output of Joint Sensor in SimMechanics. I am simulating a robot, and I need the values of joints, velocities, accelerations as well as torques. But I think the values of torques ar wrong because I have calculated their theoretical values by two different methods (I calculate the inverse dynamics model by the methods of Newton and Euler Lagrange), and the theoretical values are totally different from the values of torques from Joint Sensor . How the calculation of torques is done in Joint Sensor? Is there another way to get couples at the joints? Thank you in advance Regards Hiba
From: Guy Rouleau on 2 Jun 2010 20:35 "Hiba " <hibahage(a)hotmail.com> wrote in message <hu565j$7gt$1(a)fred.mathworks.com>... > hello, > I have a problem in the values of torque at the output of Joint Sensor in SimMechanics. I am simulating a robot, and I need the values of joints, velocities, accelerations as well as torques. But I think the values of torques ar wrong because I have calculated their theoretical values by two different methods (I calculate the inverse dynamics model by the methods of Newton and Euler Lagrange), and the theoretical values are totally different from the values of torques from Joint Sensor . > How the calculation of torques is done in Joint Sensor? > Is there another way to get couples at the joints? > > Thank you in advance > Regards > Hiba Hi Hiba, How do you drive the joint: Motion or Torque? Do you include gravity in your equations and/or model? If you are convinced the SimMechanics results, please contact technical support with an explanation about why you think the results are wrong. I will take a look at it andsee if I can explain the difference between your equations and SimMechanics. Guy
From: Hiba on 4 Jun 2010 08:04 Hi thank you for your answer I use a joint actuator that actuates the joint with motion (angular position, velocities and accelerations signals) I include gravity in the equations and in the simulator , in the machine environment block, I put [0 -9.81 0] as gravity vector without clicking the checkbox. I'm not an expert in SimMechanics, I began to use it one year ago, but I'm pretty sure of the results of my theoratical equations. I want to know, what could be wrong in my model, I'm not assuming that the default is in SimMechanics, I just want to know what could I have done wrong, or I forgot to add. Is there another way to have the values of the torques? How the joint sensor gets the torque values. I can send u my simmechanics model and the theoratical equations if u want Thanks in advance for your answer Regards Hiba
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