In order to provide a cost-effective indoor positioning and tracking service for autonomous ground vehicles and other important assets in smart factories, we report the theory and experiments for a real-time indoor positioning system using commercially available LED lamps. Inspired by the fundamental theory of the global navigation satellite system, the proposed system uses the phase difference of arrival (PDOA) approach to obtain the time difference of arrival of each carrier transmitted from individual modified LED lamps so as to estimate the receiver position. A prototype of the atto-cellular positioning system covering an area of 2.2 × 1.8 m2 with a height of 2 m was designed and experimentally demonstrated. For the design, we performed a simulation based on the Crámer–Rao bound to achieve optimal LED lamp arrangement, RF power, and other parameters. Furthermore, a virtual local oscillator for the PDOA scheme was applied to reduce the hardware complexity and to ensure the processing speed. In the experiment, the receiver was mounted on a movable material buffer station in a smart workshop, and the positioning performance was validated by tracking the trajectory of the material buffer station moving within the positioning coverage area. The experimental results show that an average positioning accuracy of ∼7 cm was achieved.
In this paper, we demonstrate a novel concept of collision avoidance based on single photon detectors along with time correlated single photon counting techniques, which uses chaotic pulse position modulation for anti-crosstalk considerations. In order to distract the signal from estimated background noise, parameters including pulse rate, discrimination threshold and number of accumulated pulses have been thoroughly analyzed based on the detection requirements, resulting in specified receiver operating characteristics curves. Both simulation and indoor experiments were performed to verify the excellent anti-crosstalk capability of the presented collision avoidance LIDAR despite of ultra-low transmitting power.
Chaotic pulse position modulation (CPPM) has been successfully used in robust digital communication for years. We propose to adapt CPPM for laser detection of remote targets to address the issue of noise. Specified in a time-of-flight (TOF) consecutive laser ranging application scenario, the feasibility of laser detection applying CPPM for laser detection is experimentally investigated. The scheme including the adaptive design for laser detection and parameter settings with validation is introduced. Lab-based electrical experiment and a proof-of-concept outdoor TOF experiment are further conducted to verify the feasibility of laser ranging and detection using CPPM through comparison with traditional Lidar detection and other pulse interval patterns. According to experiments and the following analysis, laser ranging using CPPM is feasible and more robust than traditional laser ranging.