Four-Axis Gimbal Stabilization with Segmented PID Control
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Solution Overview
Problem
Existing movie camera stabilization systems, particularly those using three- and four-degree-of-freedom gimbals, face limitations such as loss of degrees of freedom, complex adjustment requirements, and reduced accuracy under dynamic loads, especially when the first axis is not vertically oriented, leading to inefficient stabilization and control.
Innovation Solution
A four-degree-of-freedom gimbal-based stabilization and control system with two independent sub-systems, utilizing proportional-integral-derivative (PID) controllers to stabilize and control angular velocities without requiring dynamic conversions for motor torque calculations, allowing for arbitrary mounting and unlimited camera rotation around any axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a three-degree-of-freedom gimbal is used for stabilization, then the system structure is simpler, but the system loses one degree of freedom in certain orientations and requires excessively large angular accelerations near singular positions
Solution Approach 1:
The patent applies asymmetry by introducing a redundant fourth degree of freedom that breaks the symmetry of the traditional three-axis gimbal. This additional axis allows the system to avoid singular configurations where degrees of freedom are lost, ensuring reliable stabilization across all orientations without requiring excessively large angular accelerations.
Solution Approach 2:
The patent transitions from a three-degree-of-freedom system to a four-degree-of-freedom system by adding another rotational dimension. This dimensional expansion provides redundant pathways for achieving the desired camera orientation, eliminating the singularity problems that plague three-axis gimbals and enabling continuous, smooth operation in all spatial configurations.
2Reliability
If a four-degree-of-freedom gimbal is used to avoid loss of degrees of freedom, then stabilization reliability improves, but the control system complexity and adjustment difficulty increase significantly
Solution Approach 1:
The patent segments the control system into two independent subsystems: an inner loop for angular velocity stabilization and an outer loop for orientation control. This segmentation allows each subsystem to operate independently with simplified control algorithms, avoiding the need for complex dynamic conversions and inertia moment calculations that would otherwise be required for a unified four-axis control system.
Solution Approach 2:
The patent implements feedback control through two nested loops where the inner loop stabilizes angular velocities based on real-time sensor data, and the outer loop adjusts orientations based on the inner loop's performance. This feedback mechanism enables the complex four-degree-of-freedom system to operate reliably without requiring complex real-time calculations of inertia moments and dynamic conversions.
3Ease of operation
If the first axis is constrained to be vertical for correct operation, then the control algorithm is simpler, but the adaptability to different mounting configurations is reduced
Solution Approach 1:
The patent achieves universality by designing a control system that can operate in any mounting configuration without requiring the first axis to be vertical. The four-degree-of-freedom gimbal with segmented control loops can adapt to various installation orientations (vertical, horizontal, angled) and different application scenarios (cranes, drones, handheld rigs) while maintaining simplified control algorithms through its independent inner and outer loops.
4Measurement precision
If dynamic conversions are performed to determine control torques in a four-degree-of-freedom system, then the orientation control accuracy improves, but the calculation complexity and adjustment difficulty increase
Solution Approach 1:
The patent segments the control into two independent loops where the inner loop handles angular velocity stabilization with simple proportional control, and the outer loop manages orientation with variable gain scheduling. This segmentation eliminates the need for complex real-time dynamic conversions and inertia moment calculations that would otherwise be required to achieve accurate orientation control in a four-degree-of-freedom system.
Solution Approach 2:
The patent employs parameter changes by implementing variable gain scheduling in the outer loop controller, where the gain is adjusted based on the current operational state rather than performing complex dynamic conversions. This approach maintains high orientation control accuracy while significantly reducing calculation complexity and avoiding the need for real-time inertia moment determination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution simplifies the adjustment and operation of the stabilization system, enhances accuracy and dynamic performance, and expands its usage to include arbitrary mounting on cinematographic cranes, enabling unlimited camera rotation while reducing calculation complexity and component costs.
Implementation Method 1
an inertial measurement unit (1) which is mounted on a platform (23) for mounting a movie camera (22), wherein the inertial measurement unit (1) provides information about angular velocities of the movie camera (22) in a coordinate system which is associated with the movie camera (22)
Implementation Method 2
The first sub-system is made in the form of three control loops based on proportional-integral-derivative (PID)-controllers to minimize a projection of a sum of reference angular velocities and angular velocities measured by the inertial measurement unit 1 on the axis of the corresponding motor
Implementation Method 3
a first PID-controller that is a controller for minimizing a deviation of the third frame 20 from its central position and has a gain that is variable according to a cosinusoidal law depending on a relative angular position of the second frame 19 of the gimbal 17
Data Source
AI summary
The invention relates to movie camera stabilization and control systems in an inertial space, based on classic four-axes gimbal structure, that comprises four frames which are successively connected to each other and have mutually perpendicular rotation axes. In proposed embodiment camera orientation is controlled by three inner gimbal's frames that are controlled by first control sub-system and the first gimbal frame is controlled by second control subsystem. Proposed control subsystems are simple in realization, independent from each other and together with four-axes gimbal provide unrestricted orientation control of the movie camera in inertial space regardless of the gimbal mounting point orientation.