What is the processing structure of Universal Robots – Robot Controller?

1. Serial processing structure

The so-called serial processing structure means that the control algorithm of the robot is processed by the serial machine, for this type of controller, from the computer structure, control mode to divide, and can be divided into the following:

1. The single CPU structure and centralized control mode use a powerful computer to realize all the control functions, and this structure is used in the early robots, but many calculations (such as coordinate transformation) are required in the control process, so the control structure is slow.

2. The second-level CPU structure and master-slave control mode The first-level CPU is the host, which is responsible for system management, robot language compilation and human-machine interface functions, and also uses its computing power to complete coordinate transformation and trajectory interpolation, and regularly sends the calculation results to the common memory as the increment of joint movement for the second-level CPU to read; The secondary CPU completes the digital control of all joint positions. There is basically no connection between the two CPU buses of this type of system, and the data is only exchanged through the common memory, which is a loosely coupled relationship. It is difficult to further decentralize the functionality with more CPUs.

3. Multi-CPU structure and distributed control mode

At present, this kind of two-level distributed structure of upper and lower computers is widely adopted, and the upper computer is responsible for the management of the whole system, kinematic calculation, trajectory planning, etc. The lower computer is composed of multiple C PU, each CPU controls a joint movement, and the connection between these CPUs and the main controller is through tight coupling in the form of a bus, and the working speed and control performance of the controller of this structure are significantly improved. However, the common feature of these multi-CPU systems is that they are functionally distributed for specific problems, i.e., each processor takes on a fixed task, which is the structure of most commercial robot controllers in the world today.

The position control part of the controller computer control system almost invariably adopts digital position control.

The above types of controllers all use serial machines to calculate robot control algorithms, and they have a common weakness: heavy computing burden and poor real-time performance. Therefore, most of the methods such as offline planning and feedforward compensation decoupling are used to reduce the computational burden in real-time control, and when the robot is disturbed during operation, its performance will be affected, and it is more difficult to ensure the accuracy indicators required in high-speed movement.

　　Second, the parallel processing structure

Parallel processing technology is an important and effective means to improve the computing speed, can meet the real-time requirements of robot control, from the literature, about the parallel processing technology of robot controller, people have studied more parallel algorithms and their implementation of robot kinematics and dynamics.

In 1982, J. Y. S. Luh first proposed the problem of parallel processing of robot dynamics, because the dynamic equation of articulated robot is a set of nonlinear strongly coupled second-order differential equations, which is very complex to calculate, and improving the calculation speed of robot dynamics algorithm also lays the foundation for the realization of complex control algorithms such as calculation moment method, nonlinear feedforward method, adaptive control method, etc.

One of the ways to develop parallel algorithms is to transform the serial algorithm to make it parallel, and then map the algorithm to the parallel structure. The second is to first develop the parallelism of the algorithm, and then design the parallel processor structure that supports the algorithm to achieve the best parallel efficiency.

What is the processing structure of Universal Robots – Robot Controller?

What is the processing structure of Universal Robots – Robot Controller?

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