Objective Micro-vibrations generated by internal moving components during spacecraft on-orbit operations constitute a critical factor limiting the optical axis stability and imaging quality of space-based optical payloads. Isolating these disturbances and maintaining precise pointing are essential for high-precision tracking and imaging tasks. Incorporating a payload platform capable of both vibration isolation and precision pointing is considered a "multi-win" technical solution. While piezoelectric actuators are common, their limited stroke restricts millimeter-level applications. Voice coil motors (VCMs), conversely, offer large strokes and high linearity but often lack guidance in fast steering mirror applications, leading to lateral drift. Furthermore, traditional hexapod platforms based on the Gough-Stewart configuration, while accurate, involve six-degree-of-freedom fully coupled control. This introduces structural redundancy and control complexity for payloads that primarily require pitch and yaw stabilization. To address the dual requirements of vibration isolation and tracking pointing in pitch and yaw directions, a simplified quadruped platform integrated with voice coil actuation is proposed. The design targets a natural frequency of approximately 5 Hz to facilitate passive isolation of high-frequency disturbances and a pointing adjustment range of ±1° for low-frequency tracking. This study aims to balance structural simplification, large-stroke capability, and high-precision motion, providing a physical foundation for subsequent active vibration control and compound axis tracking systems.

Methods A simplified multi-degree-of-freedom parallel mechanism configuration was adopted. The platform consists of a payload platform, a base, and four supporting legs arranged symmetrically at 90° intervals along a circumference. A push-pull actuation strategy was implemented where legs 1 and 3 control pitch motion, and legs 2 and 4 control yaw motion, enabling decoupled control. VCMs were selected as actuators to leverage their zero stiffness, large stroke, and high resolution. To ensure precise axial motion and eliminate friction, a flexible guidance structure and flexure hinges were developed. A double diaphragm spring system was designed to provide low axial stiffness for actuation compliance while maintaining high radial stiffness to prevent lateral drift and contact between the coil and magnet. The diaphragm springs were designed using 60Si2Mn steel, and Finite Element Analysis (FEA) was used to verify structural integrity. A theoretical model based on dynamic principles established the relationships between leg inclination, pointing range, and resonant frequencies. FEA was further conducted to validate the design, simulating the stiffness of the diaphragm springs and performing modal analysis on a complete 3D model with a 40 kg payload to identify vibration modes. A physical prototype was manufactured, and a specific suspension system utilizing a tripod, tension springs, and flexible cords was constructed. This system effectively offloaded the gravity of the 40 kg payload to simulate a micro-gravity environment, ensuring that the platform's dynamic characteristics were tested without the bias of static gravitational forces. An experimental test system comprising accelerometers, linear optical encoders, and a frequency response analyzer was established to perform sine sweep excitations (1 Hz to 300 Hz), stroke capability tests, and decoupling verification.

Results and Discussions FEA results indicated that the double diaphragm spring configuration achieved an axial stiffness of 3.83 N/mm and a radial stiffness of 1703.87 N/mm. Stress analysis showed a maximum stress of 330.33 MPa at the spring's flexure points, which is well below the 1180 MPa yield strength of the 60Si2Mn material, resulting in a safety factor of 3.57. Simulation confirmed that a leg stroke of 2.7 mm was sufficient to achieve a platform tilt of 1°. Modal analysis predicted the first and second order modes (pitch and yaw) at 4.7413 Hz, aligning closely with the 5 Hz design target, while the third mode (Z-axis translation) appeared at 5.7381 Hz. Higher-order modes were pushed beyond 60 Hz, avoiding interference with the control bandwidth. Experimental testing on the prototype demonstrated the following: 1) Individual legs achieved a total stroke exceeding 6.8 mm. Under sinusoidal actuation, the platform successfully verified a pointing range of ±1°, meeting tracking requirements. 2) During single-axis excitation, parasitic motion in the non-driven axis was minimal. For a 2 mm pitch motion, yaw cross-coupling was approximately 2% (0.041 mm), confirming effective decoupling. 3) With a 40 kg payload, measured resonant frequencies were 5.2 Hz for pitch and 5.6 Hz for yaw. These values agree well with the FEA prediction (4.74 Hz). 4) Tests with varying loads validated the dynamic model: 20 kg load resulted in ~7 Hz resonances, and no-load conditions yielded ~16 Hz.

Conclusions A voice coil-actuated integrated vibration isolation and pointing quadruped platform was successfully designed and verified. The simplified parallel mechanism, utilizing flexure hinges and double diaphragm springs, effectively resolves the conflict between large-stroke pointing and high-precision vibration isolation. Experimental results confirmed the platform meets critical specifications: a natural frequency near 5 Hz under a 40 kg load and a pointing range of ±1°. The study demonstrates that pitch and yaw motions are effectively decoupled, and the experimental data aligns well with theoretical models. This work establishes a verified physical platform capable of passive high-frequency isolation and active low-frequency tracking. Future developments may include integrating this platform with a fast steering mirror to form a two-stage composite control system, enabling coarse tracking via the platform and fine tracking via the mirror for enhanced precision.