Rotational Position Tracking Using Circumferential LED Emitters
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Solution Overview
Problem
Existing target tracking systems for construction machines cannot determine the rotational or directional position of a single target, such as a blade on a vehicle, and require multiple targets to determine directional position, which limits accuracy.
Innovation Solution
A target with circumferentially arranged emitters, such as light emitting diodes, emits an omni-directional synchronization signal followed by sequential activation of emitters to determine the rotational position by detecting the strongest signal amplitude, allowing calculation of the target's reference direction relative to a known coordinate system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple targets are mounted on a single machine to determine rotational position, then directional position can be determined, but device complexity increases
Solution Approach 1:
The single target is segmented into multiple circumferentially arranged emitters (e.g., 8 LEDs) that can be independently controlled. Each emitter represents a discrete angular position, allowing the system to determine rotational orientation by detecting which emitter is currently facing the tracker. This segmentation enables rotational position determination with a single target instead of requiring multiple separate targets.
Solution Approach 2:
The emitters are activated in a periodic sequential manner around the circumference of the target. By cycling through emitters in a predetermined sequence and detecting the amplitude of received signals at the tracker, the system can determine angular position based on which emitter produces the strongest signal. This periodic activation pattern enables continuous rotational position monitoring.
2Device complexity
If a single target is used for tracking, then device complexity is reduced, but rotational position determination becomes impossible
Solution Approach 1:
Different emitters are positioned at different local locations around the circumference of the target, with each emitter having a specific angular position. The tracker detects which local emitter is currently oriented toward it by measuring signal amplitude, thereby determining the target's rotational position. This local differentiation of emitter positions enables angular measurement from a single target.
Solution Approach 2:
The system uses variations in light emission intensity (analogous to color changes) to encode positional information. Different emitters emit light with different amplitudes when activated, and the tracker detects these amplitude variations to determine which emitter is facing it. This intensity modulation allows the single target to convey rotational position information.
3Measurement precision
If emitters are activated sequentially to determine rotational position, then measurement precision improves, but loss of time increases
Solution Approach 1:
The emitters are pre-arranged in a fixed circumferential pattern with known angular positions. The activation sequence follows a predetermined order, and the tracker is pre-configured to expect signals in this sequence. This preliminary arrangement allows the system to quickly determine rotational position by simply detecting which emitter activates next in the sequence, reducing the time required compared to scanning or searching for the active emitter.
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 method provides improved rotational accuracy for a single target by interpolating between detected amplitudes from multiple emitters, enabling precise determination of the target's position without the need for multiple targets, enhancing tracking precision in construction and other applications.
Implementation Method 1
The target may comprise emitters, such as light emitting diodes or the like
Implementation Method 2
The target may, for example, include retro-reflecting prisms which are used as targets for an electronic distance measurement beam emitted from a total station
Data Source
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AI summary
A method for determining rotational position of a target in a target tracking System is disclosed. The target comprises a plurality of light emitting elements arranged circumferentially around the target. The target tracking System further comprises a tracker unit capable of detecting light emitted by said light emitting elements. The method comprises the Steps of emitting from said light emitting elements an omni-directional synchronization signal; detecting in the tracker unit said synchronization signal; activating said light emitting elements sequentially starting from a reference direction, wherein each light emitting element is activated for a predetermined time and emits light during the time it is activated; detecting in the tracker unit a time when a maximum amount of light is received from the target; and calculating the reference direction for the target relative to a coordinate System based on the time interval between detection of the synchronization signal and the detection of a maximum amount of light received from the target. An active target for use in the method is also disclosed.