Technical Manual for EA350 Analog Pulse Type Servo Driver V101 ➢ Associated parameter ➢ Application instance of speed feedforward When using the factory setting (5ms), the speed feedforward smoothing filter gives a play to the speed feedforward by gradually raising the speed feedforward gain.
At a given speed, the position deviation for an action may be adjusted by using the formula below Position deviation (command unit) = Speed corresponding to position command Ч (100-speed feedforward gain) Position loop gain 100 If the speed feedforward gain is set to 100%, then the position deviation in calculation is the gain; yet this will cause significant overshooting upon acceleration and deceleration. Besides, when the position command input has relatively low or non-uniform pulse frequency, speed feedforward gain may lead to great impact or noise during operation. In this case, a position command filter (inertia filter P1-14, position FIR filter P5-23) shall be used.
➢ Application instance of torque feedforward When torque feedforward is used, it is required to correctly set the load inertia ratio P4-10. It can be obtained by using offline inertia identification or based on the actual mechanical conditions. When the torque feedforward smoothing filter time constant is the factory setting (5ms), the torque feedforward gain can be gradually raised to make the torque feedforward valid. Provision of torque feedforward gain can make the position deviation at a fixed acceleration or deceleration approach to 0.
For this consideration, in the ideal condition of no external disturbing torque, position deviation in all action areas driven according to a trapezoidal speed curve can be made close to 0. In fact, external disturbing torque does exist, and therefore the position deviation cannot be 0. 6.11.2 Friction torque compensation Friction is inevitable for machines. For different machines, there are mainly three types of friction. EA350 can provide compensation against the three types of friction.
➢ Associated parameter *The reference value for friction torque compensation is the rated torque of the motor 75 Function code Parameter name Function P4-06 Speed feedforward gain The speed control command calculated based on the internal position command is multiplied by the set ratio of this parameter and then added to the speed command after position control processing. P4-07 Speed feedforward filtering time constant Set the time constant of the primary inertia filter required for speed feedforward input to reduce harmonic component in the command. P4-24 Torque feedforward gain Position control mode:
The torque command calculated based on second-order differential of the external position command is multiplied by the set ratio of this parameter and then added to the torque command after speed control processing. Speed control mode: The torque command calculated based on the internal speed command is multiplied by the set ratio of this parameter and then added to the torque command after speed control processing. P4-25 Torque feedforward filtering time constant Set the time constant of the primary inertia filter required for speed feedforward input to reduce harmonic component in the command.
Function Parameter name Function code P4-30 Friction compensation smoothing time constant Primary inertia filtering of the three types of torque compensation can prevent vibration resulted from abrupt change of the torque command; yet a too high setting may lead to slow compensation. P4-31 Viscous friction compensation gain The product of the command speed multiplied by the setting is used as the torque compensation value added to the torque command. *It is used for compensation when friction increases linearly with speed. P4-32 Added torque Addition to the torque command in a fixed direction.
When this value is positive, it suggests that the direction of the added value is the forward rotating direction of the motor, or otherwise it is the reverse rotating direction of the motor. * Only if the activation is ON, torque addition will be performed even if there is no command. P4-33 Torque compensation in the forward direction It is added to the torque command when the motor rotates in the forward direction to compensate the forward dynamic friction. *The physical direction of motor forward or backward rotation is determined by P0-01.
P4-34 Negative torque compensation It is added to the torque command when the motor rotates in the reverse direction to compensate the reverse dynamic friction