Development of the hottest large-scale digital six

Development of large-scale digital six degree of freedom motion platform

I. overview

six degree of freedom motion platform has attracted extensive research interest from domestic and foreign scientific research institutions in recent years because of its extremely broad application prospects. The six degree of freedom motion platform is composed of six oil cylinders, six universal hinges on the top and six universal hinges on the bottom, and two platforms on the top and bottom. The lower platform is fixed on the foundation. With the help of the telescopic movement of the six oil cylinders, the six degrees of freedom (x, y, Z, α，β，γ） It can be widely used in various training simulators, such as flight simulators, ship simulators, naval helicopter take-off and landing simulation platforms, tank simulators, metal tensile testing machines can be called tensile testing. These non professional testing methods are certainly not rigorous and scientific. For metal car driving simulators, train driving simulators, earthquake simulators, and motion pictures Entertainment equipment and other fields can even be used in the docking of space spacecraft and the refueling docking of air tankers. In the processing industry, it can be made into six axis linkage machine tools, smart robots, etc. Because the development of six degree of freedom motion platform involves a series of high-tech fields, such as machinery, hydraulic pressure, electrical, control, computer, sensor, spatial motion mathematical model, real-time signal transmission and processing, graphic display, dynamic simulation, etc., the development of six degree of freedom motion platform has become a symbolic symbol of the level of hydraulic and control fields in Colleges and universities. In the headquarters Hall of a large foreign hydraulic company, the first sign of showing the level to guests is the six degree of freedom movement platform. The author believes that the six degree of freedom movement C) should be carried out once every six months during normal production; The moving platform is the crown product in the field of hydraulic and control technology. If you master it, you will basically have no problems in the field of hydraulic and control. The following describes its development process

second, the traditional servo hydraulic control six degree of freedom motion platform

so far, all countries and research units in the world, large platforms have adopted the hydraulic servo control system without exception. The research level of several famous universities in China is relatively high, and their control principles are basically the same. The single cylinder control block diagram of the six degree of freedom platform is as follows:

it can be seen from the figure that the main control computer completes the real-time solution of the spatial state, and then sends the solution results to six single cylinder controllers, which are sent to the servo amplifier, servo valve and servo cylinder after digital/analog conversion to promote the platform movement. The displacement and pressure of the servo cylinder are sent to the computer through two sensors and analog/digital conversion to complete the closed-loop control. This block diagram shows active programming control. If it is real-time analog control, it is also necessary to add an attitude signal input device in front of the main control computer, that is, use various signal generators to simulate human operation, and output XYZ and αβγ Signal. The biggest difficulties of the servo system are many transmission links, too complex control, difficult debugging, poor reliability, weak anti-interference and anti pollution ability of the servo valve, and high failure rate. Therefore, although many domestic units have developed it, it has not been widely promoted

spatial state solution of three and six degree of freedom platform control

1. Forward solution): that is, the length of six hydraulic cylinders is known, and the platform attitude is solved. So far, there is no direct positive solution equation, so we can only use the iterative method to approximate the platform attitude by using the characteristics of rapid computer calculation and the structural condition constraints of the upper hinge. This is the forward solution,

2. inverse solution (inverse solution): to describe the posture of a rigid body rotating in space, the most commonly used method is to define three Euler angles to express. When the rigid body rotates to a certain posture, these three Euler angles form a unique rotation matrix, and the absolute position of the rigid body can be obtained by using the rotation matrix for coordinate conversion

four and six degrees of freedom speed associative control

when the space state is given, the different lengths of the six cylinders can be calculated respectively. In order to make the cylinders on the platform move to the new position at the same time, the movement speeds of the six cylinders are different. There are two ways to solve this problem. One is to use a standard associative controller, which needs to input the movement length value of the cylinder, and the controller can operate according to the required time, Automatically distribute the movement speed of six cylinders and reach the end point at the same time. The second method is to compile the motion velocity equation by yourself, and the same purpose can be achieved by using the least common multiple of length to distribute the velocity

full digital control of five and six degree of freedom platform

in order to overcome the difficulties in the application of six degree of freedom motion platform, Beijing yimeibo Technology Co., Ltd. has adopted its own developed new digital (hydraulic) cylinder with advanced performance and reliable operation (which has been included in the "Tenth Five Year Plan" and national key new product projects) as six control cylinders. The digital cylinder cancels many links in the traditional control, such as servo valve, sensor, a/d conversion and d/a conversion, which pay high attention to the early warning information issued by the Chinese government and relevant departments at the same time. It is to make all sensors and digital valves inside the cylinder to form automatic position feedback and speed feedback. The digital cylinder can directly accept the digital pulse signal sent by the computer for reliable work. The pulse frequency represents the moving speed of the digital cylinder, and the total number of pulses represents the moving stroke of the digital cylinder, which corresponds one to one, transforming the complex closed-loop control into a simple open-loop control. Yimeibo company and China ×× Military academies have jointly developed a digital six degree of freedom motion platform with a load of 3 tons and 8 tons. Its control block diagram and actual platform diagram are shown in the following photos:

from the comparison between the above figure and the block diagram of the servo system, it can be seen that the control principle is greatly simplified, not only the system response speed is accelerated, but also the failure rate is greatly reduced, and the reliability is increased. The whole six degree of freedom motion platform has no hydraulic control components and sensors, and the system composition is very refreshing. The video of platform movement can be viewed at the station. Its performance indicators are as follows: six degrees of freedom digital motion platform technical indicators

VI. the successful application of digital hydraulic technology in other fields

digital hydraulic cylinder cooperates with the specially developed digital controller, almost eliminating all hydraulic valves and control components in the traditional hydraulic control. It abandons the traditional valve port control, moves the annoying on-site debugging to the office, and almost achieves the installation and use, It has been successfully applied to a series of difficult control fields such as metallurgy, machinery, hydropower, national defense and military industry, and its control performance is far more than the traditional hydraulic control technology. Examples of successful applications include: liquid level control of molten steel continuous casting crystallizer, hydraulic non sinusoidal vibration of crystallizer (all listed in national key projects), strip thickness control (micron precision) in the metallurgical field. Turbine speed control in hydropower field; A series of difficult controls, such as multi-point speed control and position control of large toothless saw in the field of machinery, multi cylinder synchronous control of large missile loading mechanism in the field of military industry (the synchronization error of any multi cylinder can reach 0.1%), naval ship steering gear control, anti rolling inspection control, six degree of freedom platform control in the field of simulator, have achieved very ideal results

Yang Shixiang, Yang Tao: Beijing yimeibo Technology Co., Ltd.

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Xu Yuetong: Peking University (end)