What are the differences between vector control and VF control?

What is the difference between vector control and VF control? Many novices are not very clear about this. Vector control (Vector Field Control, referred to as VFC) and VF control (Visual Feedback Control) are two different robot control methods. Their differences are as follows:

1. Control method: The VFC control method uses vector field theory to control the robot's movement direction and speed by defining a vector field related to the robot's task in the workspace. The VF control method uses computer vision technology to obtain image information of the robot's surrounding environment through visual sensors. The computer can adjust one or more movement trajectories of the robot in real time based on changes in the environment, so that it can perform its functions effectively and safely.

2. Application areas: The VFC control method is widely used in robot path planning, obstacle avoidance and operation control, and is suitable for industrial scenes with complex environments and the control of multi-joint movements such as four-limb robots; while the VF control method is widely used in robot operation, assembly, positioning and movement, and is suitable for high-precision operation of robots with various numbers of joints in industrial production.

3. Control accuracy: The VFC control method has higher accuracy, which can improve the control accuracy of the robot movement by reducing the falling interval of the vector field and reduce the possibility of collision during robot movement; while the VF control method has lower accuracy, which can be improved by using the control range and sampling frequency of the robot's visual sensor.

4. Mechanism of action:

Vector control mechanism: Speed ​​control (ASR) during vector control operates the torque command so that the deviation between the speed command and the speed detection value (PG feedback or speed estimation value) is 0.

The mechanism of VF control: Speed ​​control during V/f control with PG operates the output frequency so that the deviation between the speed command and the speed detection value (PG feedback or speed estimation value) is 0.

5. Characteristics of both:

Characteristics of vector control: It is necessary to measure (or estimate) the speed or position of the motor. If the speed of the motor is estimated, the motor resistance and inductance parameters are required. If it is possible to use with a variety of different motors, an automatic debugging program is required to measure the motor parameters. By adjusting the control target value, the torque and flux can change quickly, which can generally be completed within 5-10 milliseconds.

Characteristics of VF control: The accuracy of torque is related to the motor parameters used in the control system. Therefore, if the rotor resistance value increases due to changes in motor temperature, the error will increase.

In summary, there are certain differences between the two control methods in terms of application scope and control accuracy. The specific application needs to be selected based on actual needs and factors such as robot structure.