Force control function
Overview of the Force Control Function
A force control function is a function to control the robot to achieve a given target force and torque using an Epson Force Sensor.
Normally, a robot moves to the given target position by position control. The force control function is used to ensure that a target force can be achieved. Furthermore, it enables the robot to perform high precision positioning and Peg In Hole tasks.
The force control function can be used in conjunction with normal CP operation commands or it can be used alone.
The force control function is performed in the specified coordinate system and can be performed independently in each of the six axes (X, Y, Z, U, V, and W). Therefore, the force control function can be enabled for all the axes at the same time or only for the specified axis.
Furthermore, since the characteristics of the force control function can be changed for each axis, it can be used for various applications; for example, the pressing operation is performed in an axis, while force is not controlled in another axis.
Parameters of the Force Control Function
The following describes the three important parameters of the force control function.
Force control with various characteristics can be performed by changing the following three parameters and target force.
Virtual inertia coefficient (Mass)
Virtual mass of the force control function. The unit is as follows.
Translation direction (Fx, Fy ,Fz): mN/(mm/sec2)
Rotation direction (Tx, Ty, Tz): mN/mm/(deg/sec2)
The mass parameter impacts the acceleration of the force control function. When the change in force is the same, decreasing the mass parameter increases the acceleration and increasing the mass parameter decreases the acceleration.Virtual viscosity coefficient (Damper)
Virtual viscosity of the force control function. The unit is as follows.
Translation direction (Fx, Fy ,Fz): N/(mm/sec)
Rotating direction (Tx, Ty, Tz): N・mm/(deg/sec)
The damper parameter impacts the speed of the force control function. Decreasing the damper parameter increases the speed and the response to changes in force, but may cause the motion of the robot to become vibratory. Conversely, increasing the damper parameter decreases the speed and suppresses the vibration, but decreases the response to changes in force.Virtual elasticity coefficient (Spring)
Virtual spring coefficient of the force control function. The unit is as follows.
Translation direction (Fx, Fy ,Fz): N/mm
Rotating direction (Tx, Ty, Tz): N・mm/(deg)
The spring parameter impacts the amount of movement of the force control function. Setting the spring parameter provides a virtual spring to limit the maximum amount of movement of the robot. Using this parameter can prevent the robot from interfering with objects around it.
Setting "0" does not limit the amount of movement. When the same constant force continues to be applied, decreasing the spring parameter increases the amount of movement, and increasing the spring parameter decreases the amount of movement.