In the fields of inertial navigation, aircraft attitude simulation and emulation, aerospace, and high-end equipment manufacturing, inertial devices (gyroscopes, accelerometers) and their constituent systems (IMU, inertial navigation) are the core of sensing motion and position. Their performance directly determines the accuracy and reliability of the entire system. The single axis inertial testing turntable is an indispensable high-precision benchmark equipment for evaluating, calibrating, and calibrating these "nerve centers". This article will delve into its core working principle and key performance indicators, showcasing its technical significance in the field of cutting-edge testing.

1、   Core working principle: Building an "ideal" motion benchmark

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 tested inertial device. Its technological implementation is the crystallization of the fusion of precision machinery, modern servo control, and high-precision sensing.

1.  Precision Machinery Body: The Physical Foundation of Performance·

Precision shaft system: High end turntables commonly use diagonal 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 positional accuracy.

Direct Drive Technology:; Abandoning traditional transmission links such as gears and worm gears, the platform is directly driven by high torque and multi pole torque motors. Its advantages lie in zero backlash, low torque fluctuations, and high dynamic response, completely eliminating the nonlinear effects caused by transmission errors and flexibility.

High rigidity and low deformation structure:; The platform and base are made of materials with low thermal expansion coefficient and symmetrically reinforced design, ensuring minimal geometric deformation and maintaining shaft stability under different loads and temperatures.

2.  High precision angle measurement system: the "eyes" of the system

The core is an ultra high precision circular grating encoder, which can have tens or even hundreds of thousands of lines engraved, and achieve sub arcseconds or even milliarcseconds of resolution through precision Moir é fringes and electronic subdivision technology. It measures the absolute position of the turntable in real-time and continuously, forming the feedback source of the fully closed-loop control, and its accuracy directly determines the positioning reference of the system.

3.  High performance servo control system: the "brain" and "nerve" of the system

This is a high-speed digital signal processor (DSP/FPGA) based system; Real time closed-loop control system. It receives motion commands from the upper computer (such as position, velocity, sine wave oscillation), compares them with the actual values fed back by the grating, and uses advanced control algorithms (such as adaptive PID, feedforward compensation, disturbance observer, notch filtering); Real time calculation and output of control variables.

Feedforward compensation: Pre compensate for the known inertia and friction of the system to improve dynamic tracking accuracy.

Notch filter: accurately suppresses mechanical resonance peaks to ensure system stability at high bandwidth.

The control signal is amplified by a high-performance servo driver to accurately drive the torque motor, forming a precise closed-loop of "instruction control drive execution feedback correction", thereby achieving smooth and precise motion from ultra-low speed to high speed.

2、   Analysis of Key Performance Indicators: Defining the Boundaries of Testing Capability

To evaluate the quality of a single axis inertial testing turntable, it is necessary to examine it from multiple dimensions such as static, dynamic, and environmental adaptability. The following indicators are the core basis for engineer selection and also represent the technical ceiling of manufacturers.

1.  Static accuracy index: measuring the scale of "stillness"

Positioning accuracy:; The maximum deviation between the instruction position and the actual stop position (unit: arcseconds). It comprehensively reflects the axis error, grating error, and steady-state control error, and is the "absolute scale" accuracy of the turntable.

Position resolution:; The minimum angle increment that the control system can recognize or execute. It determines the lower limit of motion smoothness, usually higher than positioning accuracy (such as positioning accuracy of 2 ", resolution up to 0.36").

Axis rotation error:; Including radial/axial runout, referring to the non ideal motion of the rotating axis in space. The indicator of high-precision turntable can reach ± 1 ", which is the key to ensuring that the tabletop does not shake.

2.  Dynamic performance indicators: testing the character of 'motion'

Range and stationarity of angular velocity:; This is the most core and technically challenging indicator.

Scope: Requires coverage from below the Earth's rotation rate level (0.001 °/s); ）Extreme span up to high-speed maneuvering level (± 10000 °/s).

Rate stationarity: The fluctuation of instantaneous rate relative to the average rate during constant speed operation, commonly expressed as a relative value (e.g; 1×10?? ）. It directly determines the purity of the injected angular velocity in gyroscope calibration testing, and is the ultimate manifestation of evaluating the ability of the turntable servo system to suppress torque fluctuations and friction 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 frequency upper limit (in Hz) at which the turntable can accurately reproduce sinusoidal motion commands. High bandwidth means being able to simulate high-frequency attitude jitter of aircraft more realistically, which is a prerequisite for testing the dynamic response characteristics of the device.

3.  Load and universality indicators

Load capacity and inertia adaptation: not only focus on maximum load-bearing capacity, but also pay attention to the matching degree between load inertia and turntable rotor inertia. Reasonable matching is the 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), ensuring precise synchronization of turntable motion with external data acquisition systems' timestamps. This is the foundation for conducting complex experiments such as integrated navigation and multi axis testing.

Summary: Technology Selection and Value Reflection

Choosing an inertial testing turntable is not simply about pursuing the highest value of a single indicator, but about accurately matching based on the characteristics of the tested device (such as fiber optic gyroscope, MEMS IMU, laser gyroscope) and testing tasks (zero bias calibration, scale factor testing, dynamic environment simulation).

Testing laser gyroscope/high-precision fiber optic gyroscope requires the ultimate pursuit of smoothness and extremely low angular vibration at ultra-low speed rates.

Testing tactical grade MEMS IMUs or guidance heads places greater emphasis on high bandwidth, high acceleration, and the ability to reproduce complex motion trajectories.

As a key measuring 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 downstream device accuracy ceilings. It is not only a cold device, but also a "craftsman" and "gatekeeper" who promotes the progress of inertial technology and ensures the accuracy of national high-end equipment.

Jiujiang Ruyang Precision Technology Co., Ltd. is deeply engaged in the field of high-precision inertial testing turntables, committed to providing users with comprehensive solutions from standard single axis to complex multi axis systems. With first-class accuracy, excellent reliability and open system architecture, our products serve many State Key Laboratory and industry leading enterprises, and are your trusted inertial test technology partners.