In the fields of inertial navigation, aircraft attitude simulation, aerospace, and high-end equipment manufacturing, inertial devices (gyroscopes, accelerometers) and the systems they comprise (IMUs, inertial navigation systems) are the core of sensing motion and position. Their performance directly determines the accuracy and reliability of the entire system. A single-axis inertial test turntable is an indispensable high-precision benchmark device for evaluating, calibrating, and standardizing these "nerve centers." This article will delve into its core working principles and key performance indicators, showcasing its technological significance in cutting-edge testing fields.
I. Core Working Principle: Constructing an "ideal" motion reference
The essence of an inertial testing turntable is to provide a known, highly accurate, and controllable single-degree-of-freedom rotational motion environment for the inertial device under test. Its technological realization is the culmination of the integration of precision mechanics, modern servo control, and high-precision sensing.
1. Precision mechanical body: the physical foundation of performance
Precision shaft system: High-end turntables generally use paired angular contact ball bearings to meet the requirements of precision axial and radial positioning , high rigidity and high rotational accuracy . This is the physical basis for achieving ultra-low speed stability and ultra-high position accuracy.
Direct drive technology: This technology eliminates traditional gear and worm gear transmission components, using a high-torque, multi-pole motor to directly drive the platform. Its advantages include zero backlash, low torque ripple, and high dynamic response, completely eliminating the nonlinear effects of transmission errors and flexibility.
High rigidity and low deformation structure: The platform and base are made of materials with low thermal expansion coefficient and symmetrical reinforcement design to ensure minimal geometric deformation under different loads and temperatures, thus maintaining the stability of the shaft system.
2. High-precision angle measurement system: the system's "eyes"
The core component is an ultra-high precision circular grating encoder, with tens or even hundreds of thousands of lines. Through precision moiré fringes and electronic subdivision technology, it achieves sub-arcsecond or even milliarcsecond resolution. It measures the absolute position of the turntable in real time and continuously, forming the feedback source for the fully closed-loop control. Its accuracy directly determines the positioning reference of the system.
3. High-performance servo control system: the system's "brain" and "nerves"
This is a real-time closed-loop control system based on a high-speed digital signal processor (DSP/FPGA). It receives motion commands (such as position, speed, and sinusoidal swing) from the host computer, compares them with the actual values from the grating feedback, and calculates and outputs control quantities in real time using advanced control algorithms (such as adaptive PID, feedforward compensation, disturbance observer, and notch filtering).
Feedforward compensation: Pre-compensates for the known inertia and friction of the system, improving dynamic tracking accuracy.
Notch filter: Precisely suppresses mechanical resonance peaks, ensuring system stability under high bandwidth.
The control signal is amplified by a high-performance servo driver and precisely drives the torque motor, forming a precise closed loop of "command-control-drive-execution-feedback-correction", thereby achieving smooth and precise motion from ultra-low speed to high speed.
II. Key Performance Indicator Analysis: Defining the Boundaries of Test Capabilities
Evaluating the quality of a single-axis inertial testing turntable requires consideration from multiple dimensions, including static, dynamic, and environmental adaptability. The following indicators are core criteria for engineers' selection and also represent the technological ceiling of the manufacturer.
1. Static accuracy indicators: Measured by "static" standards.
Positioning accuracy: The maximum deviation between the commanded position and the actual stopping position (unit: arcseconds″). It comprehensively reflects the shaft system error, grating error, and control steady-state error, and is the "absolute ruler" accuracy of the turntable.
Position resolution: The smallest angular increment that the control system can recognize or execute. It determines the lower limit of motion smoothness and is usually higher than positioning accuracy (e.g., a positioning accuracy of 2 ″ can have a resolution of 0.36 ″ ).
Shaft rotation error: This includes radial/axial runout, referring to the non-ideal movement of the rotation axis in space. High-precision turntables can achieve this parameter of ±1″, which is crucial for ensuring the table surface remains stable.
2. Dynamic performance indicators: testing the character of "movement".
Angular rate range and stability: These are the most critical and technically challenging indicators.
Range: It needs to cover the extreme range from below the Earth's rotation rate (0.001 ° /s) to the high-speed maneuvering rate (±10000 °/s).
Rate stability: During constant-speed operation, the fluctuation of instantaneous rate relative to the average rate is commonly expressed as a relative value (e.g., 1×10⁻⁶). It directly determines the "purity" of the injected angular rate in gyroscope calibration testing and is the ultimate indicator of the turntable servo system's ability to suppress torque fluctuations and frictional disturbances.
Angular acceleration and system bandwidth:
Maximum angular acceleration: determined by the peak torque of the motor and the total inertia of the system, affecting the simulated high-dynamic maneuverability.
Servo bandwidth: The upper limit of the frequency (unit: Hz) at which the turntable can accurately reproduce sinusoidal motion commands. High bandwidth means that it can more realistically simulate the high-frequency attitude jitter of an aircraft, which is a prerequisite for testing the dynamic response characteristics of the device.
3. Load and versatility indicators
Load capacity and inertia matching: It's not enough to focus solely on the maximum load capacity; the matching degree between the load inertia and the turntable rotor inertia is crucial. A proper match is key to ensuring that dynamic performance does not deteriorate.
Synchronization and Communication Interface: Supports PPS (pulse per second) hardware synchronization and high-bandwidth real-time industrial Ethernet (such as EtherCAT) to ensure accurate synchronization between the turntable movement and the timestamp of the external data acquisition system. This is the foundation for conducting complex experiments such as integrated navigation and multi-axis testing.
Summary: Technology Selection and Value Realization
Choosing an inertial test turntable is not simply about pursuing the highest value for a single indicator, but about making a precise match based on the characteristics of the device under test (such as fiber optic gyroscopes, MEMS IMUs, and laser gyroscopes) and the test task (zero bias calibration, scale factor testing, and dynamic environment simulation).
Testing laser gyroscopes/high-precision fiber optic gyroscopes requires an extreme pursuit of stability at ultra-low speeds and extremely low angular vibration.
When testing tactical-grade MEMS IMUs or seekers, high bandwidth, high acceleration, and the ability to reproduce complex motion trajectories are of greater importance.
As a key metrology and testing equipment in the upstream of the inertial technology industry chain, the performance of the inertial testing turntable directly affects the establishment and verification capabilities of the accuracy ceiling of downstream devices. It is not only a cold piece of equipment, but also a "craftsman" and "gatekeeper" that promotes the progress of inertial technology and ensures the accuracy of the country's high-end equipment.
Jiujiang Ruya Precision Technology Co., Ltd. specializes in high-precision inertial testing turntables, committed to providing users with comprehensive solutions ranging from standard single-axis to complex multi-axis systems. Our products, characterized by top-tier precision, superior reliability, and an open system architecture, serve numerous national key laboratories and leading industry enterprises, making us a trustworthy partner for inertial testing technology.
In the fields of inertial navigation, aircraft attitude simulation, aerospace, and high-end equipment manufacturing, inertial devices (gyroscopes, accelerometers) and the systems they comprise (IMUs, inertial navigation systems) are the core of sensing motion and position. Their performance directly determines the accuracy and reliability of the entire system. A single-axis inertial test turntable is an indispensable high-precision benchmark device for evaluating, calibrating, and standardizing these "nerve centers." This article will delve into its core working principles and key performance indicators, showcasing its technological significance in cutting-edge testing fields.
I. Core Working Principle: Constructing an "ideal" motion reference
The essence of an inertial testing turntable is to provide a known, highly accurate, and controllable single-degree-of-freedom rotational motion environment for the inertial device under test. Its technological realization is the culmination of the integration of precision mechanics, modern servo control, and high-precision sensing.
1. Precision mechanical body: the physical foundation of performance
Precision shaft system: High-end turntables generally use paired angular contact ball bearings to meet the requirements of precision axial and radial positioning , high rigidity and high rotational accuracy . This is the physical basis for achieving ultra-low speed stability and ultra-high position accuracy.
Direct drive technology: This technology eliminates traditional gear and worm gear transmission components, using a high-torque, multi-pole motor to directly drive the platform. Its advantages include zero backlash, low torque ripple, and high dynamic response, completely eliminating the nonlinear effects of transmission errors and flexibility.
High rigidity and low deformation structure: The platform and base are made of materials with low thermal expansion coefficient and symmetrical reinforcement design to ensure minimal geometric deformation under different loads and temperatures, thus maintaining the stability of the shaft system.
2. High-precision angle measurement system: the system's "eyes"
The core component is an ultra-high precision circular grating encoder, with tens or even hundreds of thousands of lines. Through precision moiré fringes and electronic subdivision technology, it achieves sub-arcsecond or even milliarcsecond resolution. It measures the absolute position of the turntable in real time and continuously, forming the feedback source for the fully closed-loop control. Its accuracy directly determines the positioning reference of the system.
3. High-performance servo control system: the system's "brain" and "nerves"
This is a real-time closed-loop control system based on a high-speed digital signal processor (DSP/FPGA). It receives motion commands (such as position, speed, and sinusoidal swing) from the host computer, compares them with the actual values from the grating feedback, and calculates and outputs control quantities in real time using advanced control algorithms (such as adaptive PID, feedforward compensation, disturbance observer, and notch filtering).
Feedforward compensation: Pre-compensates for the known inertia and friction of the system, improving dynamic tracking accuracy.
Notch filter: Precisely suppresses mechanical resonance peaks, ensuring system stability under high bandwidth.
The control signal is amplified by a high-performance servo driver and precisely drives the torque motor, forming a precise closed loop of "command-control-drive-execution-feedback-correction", thereby achieving smooth and precise motion from ultra-low speed to high speed.
II. Key Performance Indicator Analysis: Defining the Boundaries of Test Capabilities
Evaluating the quality of a single-axis inertial testing turntable requires consideration from multiple dimensions, including static, dynamic, and environmental adaptability. The following indicators are core criteria for engineers' selection and also represent the technological ceiling of the manufacturer.
1. Static accuracy indicators: Measured by "static" standards.
Positioning accuracy: The maximum deviation between the commanded position and the actual stopping position (unit: arcseconds″). It comprehensively reflects the shaft system error, grating error, and control steady-state error, and is the "absolute ruler" accuracy of the turntable.
Position resolution: The smallest angular increment that the control system can recognize or execute. It determines the lower limit of motion smoothness and is usually higher than positioning accuracy (e.g., a positioning accuracy of 2 ″ can have a resolution of 0.36 ″ ).
Shaft rotation error: This includes radial/axial runout, referring to the non-ideal movement of the rotation axis in space. High-precision turntables can achieve this parameter of ±1″, which is crucial for ensuring the table surface remains stable.
2. Dynamic performance indicators: testing the character of "movement".
Angular rate range and stability: These are the most critical and technically challenging indicators.
Range: It needs to cover the extreme range from below the Earth's rotation rate (0.001 ° /s) to the high-speed maneuvering rate (±10000 °/s).
Rate stability: During constant-speed operation, the fluctuation of instantaneous rate relative to the average rate is commonly expressed as a relative value (e.g., 1×10⁻⁶). It directly determines the "purity" of the injected angular rate in gyroscope calibration testing and is the ultimate indicator of the turntable servo system's ability to suppress torque fluctuations and frictional disturbances.
Angular acceleration and system bandwidth:
Maximum angular acceleration: determined by the peak torque of the motor and the total inertia of the system, affecting the simulated high-dynamic maneuverability.
Servo bandwidth: The upper limit of the frequency (unit: Hz) at which the turntable can accurately reproduce sinusoidal motion commands. High bandwidth means that it can more realistically simulate the high-frequency attitude jitter of an aircraft, which is a prerequisite for testing the dynamic response characteristics of the device.
3. Load and versatility indicators
Load capacity and inertia matching: It's not enough to focus solely on the maximum load capacity; the matching degree between the load inertia and the turntable rotor inertia is crucial. A proper match is key to ensuring that dynamic performance does not deteriorate.
Synchronization and Communication Interface: Supports PPS (pulse per second) hardware synchronization and high-bandwidth real-time industrial Ethernet (such as EtherCAT) to ensure accurate synchronization between the turntable movement and the timestamp of the external data acquisition system. This is the foundation for conducting complex experiments such as integrated navigation and multi-axis testing.
Summary: Technology Selection and Value Realization
Choosing an inertial test turntable is not simply about pursuing the highest value for a single indicator, but about making a precise match based on the characteristics of the device under test (such as fiber optic gyroscopes, MEMS IMUs, and laser gyroscopes) and the test task (zero bias calibration, scale factor testing, and dynamic environment simulation).
Testing laser gyroscopes/high-precision fiber optic gyroscopes requires an extreme pursuit of stability at ultra-low speeds and extremely low angular vibration.
When testing tactical-grade MEMS IMUs or seekers, high bandwidth, high acceleration, and the ability to reproduce complex motion trajectories are of greater importance.
As a key metrology and testing equipment in the upstream of the inertial technology industry chain, the performance of the inertial testing turntable directly affects the establishment and verification capabilities of the accuracy ceiling of downstream devices. It is not only a cold piece of equipment, but also a "craftsman" and "gatekeeper" that promotes the progress of inertial technology and ensures the accuracy of the country's high-end equipment.
Jiujiang Ruya Precision Technology Co., Ltd. specializes in high-precision inertial testing turntables, committed to providing users with comprehensive solutions ranging from standard single-axis to complex multi-axis systems. Our products, characterized by top-tier precision, superior reliability, and an open system architecture, serve numerous national key laboratories and leading industry enterprises, making us a trustworthy partner for inertial testing technology.
