1. Design Concept
As a modern device integrating optics, mechanics, and electronics, turntables play a crucial role in semi-physical simulation and testing in the aviation and aerospace fields. They simulate various attitude angle movements of aircraft in laboratory conditions, reproducing their dynamic characteristics. This is vital for testing the flight control systems, guidance systems, and relevant components of aircraft. Through repeated testing and obtaining sufficient experimental data, systems can be redesigned and improved to meet the ideal performance requirements of the aircraft's overall design.
To understand the design and implementation of a high-precision two-dimensional servo turntable system, it is necessary to delve into the working principles and system composition of the two-dimensional servo turntable. This includes the overall system design, error analysis, hardware design, software design, and control algorithm design.
2. Development Status
Internationally, due to the widespread importance of inertial guidance technology, turntables have received significant attention from technically advanced and developing countries. Countries such as the United States, Russia, the United Kingdom, France, Switzerland, China, India, etc., have invested considerable funds and manpower in turntable development. The United States has consistently maintained a leading position in turntable research, and other countries like Germany, the UK, France, and Switzerland have achieved representative results, with performance and quality second only to the United States.
The world's first turntable was successfully developed in 1945 by the Instrumentation Lab at MIT, known as the A-type turntable. It used ordinary ball bearings, driven by an AC torque motor, and the angular position measuring element used ball and microswitch. However, due to the lower precision of the components used and a lack of reference experience, this turntable had many drawbacks, and its accuracy could only reach the degree-minute level, without practical use. Subsequently, the T-800 servo turntable developed by Ficker System, a subsidiary of Owens in Illinois, USA, marked a new level of turntable design in the United States. In the 1960s, significant improvements were made to key components of turntables worldwide, such as bearings, drive motors, and monitoring elements. Special air bearings and hydraulic bearings were successfully developed for turntables with large speed ratios and high precision. High-speed, high-precision hydraulic motors and high-resolution detection elements were born, pushing the technical level of turntables to a new level. Meanwhile, some companies specializing in turntable production emerged, such as the Contraves-Goerz Corporation (now reorganized), Carco Electronics (now part of the European Acutronic company), and Germany's MBB.
3. Domestic Development
Although China started later in turntable development compared to developed countries, it has made significant progress in recent years. Especially in recent years, the development of turntables in China has seen considerable growth. Many research institutions and universities in China, such as Harbin Institute of Technology, AVIC 303 Institute, AVIC 6354 Institute, Nanjing University of Aeronautics and Astronautics, etc., are actively engaged in turntable research and development. China independently developed and manufactured the first hydraulic flight simulation turntable in the 1960s, making significant contributions to the early development of aircraft control and guidance systems in China. In the late 1980s, China introduced digital control technology into turntable control, bringing software-based complex control laws into play. This facilitated parameter adjustments compared to analog controllers and brought China's turntable research and development into a new era. In 1990, AVIC 303 Institute successfully developed the SGT 1 three-axis strapdown inertial navigation test turntable, the first computer-controlled high-precision three-axis inertial navigation test platform in China.
Since the 1990s, the development of turntables has entered an era with higher requirements for both digital and analog aspects. This poses higher challenges for the design and tuning of turntables. Despite this, various research institutions and universities in China have achieved remarkable results in multiple directions, showcasing promising achievements. While there is still room for improvement in aspects such as structural lightweighting, high rigidity, and high precision, the achievements indicate China's remarkable progress in independent research and development.
4. Turntable Classification
Flight simulation turntables are indispensable key equipment in semi-physical flight simulation test systems. They can simulate various attitudes of aircraft in the air and reproduce their dynamic characteristics. According to different classification methods, flight simulation turntables can be divided into electric turntables and electro-hydraulic turntables, analog control turntables, digital control turntables, and mixed analog-digital control turntables, as well as single-axis, double-axis, and three-axis turntables.
5. Turntable Functions
Turntable systems
possess several crucial functions, ensuring stability, accuracy, and safety during simulation and testing:
- Rotary angle position servo control: Works in position servo control mode, adjusting positions according to given position commands and maintaining good frequency response quality.
- Rotary angle velocity servo control: Operates in velocity servo control mode, adjusting velocities according to given velocity commands and maintaining the required frequency response quality.
- Turntable limit warning: Has both soft limits, set arbitrarily through software programs, and hard limits, implemented by limit switches installed on the table body, to issue limit warning indications and protection commands.
- Turntable protection warning: Protects against amplifier failures, overruns, manual emergencies, etc. When protection is triggered, the control loop of the turntable switches to low gain, the input to the position loop becomes zero, the servo power supply to the power amplifier is cut off, and the servo motor is disconnected from the power amplifier.
- Real-time display of rotary angle: Provides real-time numerical display of the turntable angle, typically with a resolution of 0.01°.
- Microcomputer monitoring: Utilizes microcomputer digital control with the capability to interface with an upper-level microcomputer. The turntable controller can accept commands from a monitor or an upper-level microcomputer and transmit the turntable position to the upper-level microcomputer.
- Emergency stop: In case of abnormal situations or when deemed necessary by the operator, the emergency key can be pressed to put the turntable into emergency stop mode, where it performs the same control and protection actions as in emergency situations.
These functions ensure the stability, accuracy, and safety of the turntable during simulation and testing, making it an indispensable and essential tool in the development and testing of aircraft.
