scholarly journals An Improved Single-Epoch Attitude Determination Method for Low-Cost Single-Frequency GNSS Receivers

2021 ◽  
Vol 13 (14) ◽  
pp. 2746
Author(s):  
Xinzhe Wang ◽  
Yinbin Yao ◽  
Chaoqian Xu ◽  
Yinzhi Zhao ◽  
Huan Zhang
Keyword(s):  
Degrees Of Freedom ◽  
High Efficiency ◽  
Attitude Determination ◽  
Search Algorithm ◽  
Low Cost ◽  
Single Frequency ◽  
Baseline Length ◽  
Short Baseline ◽  
Cycle Slips ◽  
Ambiguity Fixing

GNSS attitude determination has been widely used in various navigation and positioning applications, due to its advantages of low cost and high efficiency. The navigation positioning and attitude determination modules in the consumer market mostly use low-cost receivers and face many problems such as large multipath effects, frequent cycle slips and even loss of locks. Ambiguity fixing is the key to GNSS attitude determination and will face more challenges in the complex urban environment. Based on the CLAMBDA algorithm, this paper proposes a CLAMBDA-search algorithm based on the multi-baseline GNSS model. This algorithm improves the existing CLAMBDA method through a fixed geometry constraint among baselines in the vehicle coordinate system. A fixed single-baseline solution reduces two degrees of freedom of vehicle rigid body, and a global minimization search for the ambiguity objective function in the other degree of freedom is conducted to calculate the baseline vector and its Euler angles. In addition, in order to make up for the shortcomings of short baseline ambiguity in complex environments, this paper proposes different validation strategies. Using three low-cost receivers (ublox M8T) and patch antennas, static and dynamic on-board experiments with different baseline length set-ups were carried out in different environments. Both the experiments prove that the method proposed in this paper has greatly improved the ambiguity fixing performance and also the Euler angle calculation accuracy, with an acceptable calculation burden. It is a practical vehicle-mounted attitude determination algorithm.

An Efficient Volumetric-Error Measurement Method for Five-Axis Machine Tools

2005 ◽  
Author(s):  
Shih-Ming Wang ◽  
Han-Jen Yu ◽  
Hung-Wei Liao
Keyword(s):  
Machine Tools ◽  
Measurement Method ◽  
Degrees Of Freedom ◽  
High Efficiency ◽  
Low Cost ◽  
Volumetric Errors ◽  
Different Types ◽  
Measurement Methodology ◽  
Simple Measurement ◽  
Five Axis

Accurate measurement of volumetric errors plays an important role for error compensation for multi-axis machines. The error measurements for volumetric errors of five-axis machines are usually very complex and costly than that for three-axis machines. In this study, a direct and simple measurement method using telescoping ball-bar system for volumetric errors for different types of five-axis machines was developed. The method using two-step measurement methodology and incorporating with derived error models, can quickly determine the five degrees-of-freedom (DOF) volumetric errors of five-axis machine tools. Comparing to most of the current used measurement methods, the proposed method provides the advantages of low cost, high efficiency, easy setup, and high accuracy.

scholarly journals An Improved Ambiguity-Free Method for Precise GNSS Positioning with Utilizing Single Frequency Receivers

Sensors ◽  
2020 ◽  
Vol 20 (3) ◽  
pp. 856 ◽  
Author(s):  
Wenhao Yang ◽  
Yue Liu ◽  
Fanming Liu
Keyword(s):  
Global Optimum ◽  
Ambiguity Function ◽  
Single Frequency ◽  
Density Estimator ◽  
New Approach ◽  
Gnss Positioning ◽  
Cycle Slips ◽  
Computation Efficiency ◽  
Ambiguity Fixing ◽  
Computation Load

The solution of carrier phase ambiguity is essential for precise global navigation satellite system (GNSS) positioning. Methods of searching in the coordinate domain show their advantage over the methods based on ambiguity fixing, for example, immune to cycle slips, far fewer epochs taken for obtaining the precise solution. However, there are still some drawbacks via using the Ambiguity Function Method (AFM), such as low computation efficiency and the existence of a false global optimum. The false global optimum is a situation where the Least Square (LS) criterion achieves minimum in another place than the point of the actual position, which restricts the application of this method to single-frequency receivers. The numerical search approach derived in this paper is based on the Modified Ambiguity Function Approach (MAFA). It focuses on eliminating the false optimum solution and reducing the computation load by utilizing single-frequency receivers without solving the ambiguity fixing problem. An improved segmented simulated annealing method is used to decrease the computation load while the Kernel Density Estimator (KDE) method is used to filter out the false optimum candidates. Static experiments were carried out to evaluate the performance of the new approach. It is shown that a precise result can be obtained by handling two epochs of data with z coordinate fixed to the referenced value. Meanwhile, the new approach can achieve a millimeter level of position accuracy after dealing with nineteen epochs of observations data when searching in x , y , z domain. The new approach shows its robustness even if the search region is broad, and the prior position is several meters away from the referenced value.

A Ball-Bar Based Error Measurement Method for a RRTTT-Type Five-Axis Machine Tool

2010 ◽  
Vol 126-128 ◽  
pp. 785-790 ◽  
Author(s):  
Shih Ming Wang ◽  
Han Jen Yu ◽  
Da Fan Chen
Keyword(s):  
Machine Tools ◽  
Measurement Method ◽  
Degrees Of Freedom ◽  
High Efficiency ◽  
Low Cost ◽  
Measurement Methods ◽  
Error Measurement ◽  
Volumetric Errors ◽  
Ball Bar ◽  
Five Axis

Measurement method using telescoping ball-bar that can directly determine the volumetric errors of three main types of five-axis machine tools was developed. Adopting Single Socket method, and the method following the defined two-step measurements sequence and incorporating with derived error models, can quickly determine the five degrees-of-freedom (DOF) volumetric errors of five-axis machine tools. Comparing to most of the current used measurement methods, the proposed method provides the advantages of low cost, high efficiency, easy setup, and high accuracy.

scholarly journals A Low-Cost INS-Integratable GNSS Ultra-Short Baseline Attitude Determination System

Sensors ◽  
2018 ◽  
Vol 18 (7) ◽  
pp. 2114 ◽  
Author(s):  
Wenyi Li ◽  
Peirong Fan ◽  
Xiaowei Cui ◽  
Sihao Zhao ◽  
Tianyi Ma ◽  
...  
Keyword(s):  
Attitude Determination ◽  
Low Cost ◽  
Short Baseline ◽  
Determination System

scholarly journals Iterative Learning Method for In-Flight Auto-Tuning of UAV Controllers Based on Basic Sensory Information

2019 ◽  
Vol 9 (4) ◽  
pp. 648 ◽  
Author(s):  
Wojciech Giernacki
Keyword(s):  
Control Systems ◽  
Performance Index ◽  
High Efficiency ◽  
Search Algorithm ◽  
Low Cost ◽  
Sensory Information ◽  
Learning Method ◽  
Comprehensive Description ◽  
Auto Tuning ◽  
The Impact

With an increasing number of multirotor unmanned aerial vehicles (UAVs), solutions supporting the improvement in their precision of operation and safety of autonomous flights are gaining importance. They are particularly crucial in transportation tasks, where control systems are required to provide a stable and controllable flight in various environmental conditions, especially after changing the total mass of the UAV (by adding extra load). In the paper, the problem of using only available basic sensory information for fast, locally best, iterative real-time auto-tuning of parameters of fixed-gain altitude controllers is considered. The machine learning method proposed for this purpose is based on a modified zero-order optimization algorithm (golden-search algorithm) and bootstrapping technique. It has been validated in numerous simulations and real-world experiments in terms of its effectiveness in such aspects as: the impact of environmental disturbances (wind gusts); flight with change in mass; and change of sensory information sources in the auto-tuning procedure. The main advantage of the proposed method is that for the trajectory primitives repeatedly followed by an UAV (for programmed controller gains), the method effectively minimizes the selected performance index (cost function). Such a performance index might, e.g., express indirect requirements about tracking quality and energy expenditure. In the paper, a comprehensive description of the method, as well as a wide discussion of the results obtained from experiments conducted in the AeroLab for a low-cost UAV (Bebop 2), are included. The results have confirmed high efficiency of the method at the expected, low computational complexity.

scholarly journals Network-based RTK Performance for Drone Navigation

2019 ◽  
Vol 94 ◽  
pp. 01006 ◽  
Author(s):  
Tae-Suk Bae
Keyword(s):  
Low Cost ◽  
Vertical Component ◽  
Single Frequency ◽  
Baseline Length ◽  
Virtual Reference ◽  
Moving Vehicles ◽  
Vertical Error ◽  
Single Baseline ◽  
Error Behavior ◽  
Gnss Data

The Real-time Kinematic (RTK) was predominantly used for the positioning of the ground applications including moving vehicles. Due to the limited baseline lengths, the Network-based RTK (NRTK) was introduced since late-1990s, and successfully applied to the high precision surveying purposes for more than a decade. We conducted the experiments to analyze the performance of the single-baseline RTK (SRTK) as well as the NRTK using one of the operational NRTK systems of Korea, which is the Virtual Reference Stations (VRS) technique. A total of 46 Continuously Operating Reference Stations (CORS) are used for both SRTK and NRTK to secure the redundancy of the baseline lengths. Since the CORS are quite evenly located at an average of 50-60 km, the analysis of error behavior is restricted in terms of seamless variation of baseline length. Therefore, on top of the existing CORS, we simulated the GNSS RINEX data of the rover (that is, the drone position) at a specific location to get the uniform distribution to the reference stations. Furthermore, the rover was generated for different altitude to evaluate the performance of vertical component of the NRTK system. The CORS GNSS data were obtained at 1 Hz in RINEX format, and the low-cost receiver (ublox) was used for the rover with same interval, single-frequency capability. The correction information from the NRTK server was simultaneously logged for post-processing using the open source software RTKLIB. The percentage of ambiguity resolution was quite reasonable up to 50 km, and drastically drops down as the baseline gets longer. The generated VRS was located with an offset of a few meters in a certain direction, and the horizontal errors also showed a similar pattern. The vertical error behavior due to the tropospheric model deficiency should also be analyzed further.

Precise Single-Frequency Positioning Using Low-Cost Receiver with the Aid of Lane-Level Map Matching for Land Vehicle Navigation

2020 ◽  
pp. 1-14
Author(s):  
Fei Liu ◽  
Yue Liu ◽  
Zhixi Nie ◽  
Yang Gao
Keyword(s):  
Low Cost ◽  
Digital Camera ◽  
Satellite System ◽  
Single Frequency ◽  
Map Matching ◽  
Digital Map ◽  
The Road ◽  
Ambiguity Fixing ◽  
Wide Range ◽  
Global Navigation Satellite

Precise positioning with low-cost single-frequency global navigation satellite system (GNSS) receivers has great potential in a wide range of applications because of its low price and improved accuracy. However, challenges remain in achieving reliable and accurate solutions using low-cost receivers. For instance, the successful ambiguity fixing rate could be low for real-time kinematic (RTK) while large errors may occur in precise point positioning (PPP) in some scenarios (e.g., trees along the road). To solve the problems, this paper proposes a method with the aid of additional lane-level digital map information to improve the accuracy and reliability of RTK and PPP solutions. In the method, a digital camera will be applied for lane recognition and the positioning solution from a low-cost receiver will be projected to the digital map lane link. With the projected point position as a constraint, the RTK ambiguity fixing rate and PPP performance can be enhanced. A field kinematic test was conducted to verify the improvement of the RTK and PPP solutions with the aid of map matching. The results show that the RTK ambiguity fixing rate can be increased and the PPP positioning error can be reduced by map matching.

scholarly journals Receiver Time Misalignment Correction for GPS-based Attitude Determination

2015 ◽  
Vol 68 (4) ◽  
pp. 646-664 ◽  
Author(s):  
Xiaohong Zhang ◽  
Mingkui Wu ◽  
Wanke Liu
Keyword(s):  
Global Positioning System ◽  
Attitude Determination ◽  
Low Cost ◽  
Baseline Length ◽  
Test Results ◽  
System A ◽  
Global Positioning ◽  
Determination System ◽  
Commercial Off The Shelf ◽  
Baseline Estimation

A prerequisite for a Global Positioning System (GPS) attitude determination is to calculate baselines between antennae with accuracy at the millimetre level simultaneously. However, in order to have a low cost attitude determination system, a set of Commercial-Off-The-Shelf (COTS) receivers with separate clocks are used. In this case, if the receiver clocks are not precisely synchronized, the baseline vector between antennae will be calculated from the GPS signals received at different times. This can be a significant error source for high-kinematic applications. In this paper, two equivalent and effective approaches are developed to compensate this significant bias for baseline estimation and attitude determination. Test results using real airborne GPS data demonstrate that the receiver time misalignment between the two receivers can result in a 5 cm baseline offset for an aircraft with a 50 m/s velocity; the corresponding attitude errors can reach about 0·50° in yaw and 0·10° in pitch respectively for the attitude determination system with a baseline length of 3·79 m. With the proposed methods, these errors can be effectively eliminated.

scholarly journals Research on Tightly Coupled Multi-Antenna GNSS/MEMS Single-Frequency Single-Epoch Attitude Determination in Urban Environment

2021 ◽  
Vol 13 (14) ◽  
pp. 2710
Author(s):  
Ming Gao ◽  
Genyou Liu ◽  
Shengliang Wang ◽  
Gongwei Xiao ◽  
Wenhao Zhao ◽  
...  
Keyword(s):  
Success Rate ◽  
Ambiguity Resolution ◽  
Urban Areas ◽  
Attitude Determination ◽  
Integer Ambiguity ◽  
Single Frequency ◽  
Half Cycle ◽  
Cycle Slips ◽  
Tightly Coupled ◽  
Single Epoch

GNSS-only attitude determination is difficult to perform well in poor-satellite-tracking environments such as urban areas with high and dense buildings or trees. In addition, it is harder to resolve integer ambiguity in the case of single-frequency single-epoch process mode. In this contribution, a low-cost MEMS gyroscope is integrated with multi-antenna GNSS to improve the performance of the attitude determination. A new tightly coupled (TC) model is proposed, which uses a single filter to achieve the optimal estimation of attitude drift, gyro biases and ambiguities. In addition, a MEMS-Attitude-aided Quality-Control method (MAQC) for GNSS observations is designed to eliminate both the carrier multipath errors and half-cycle slips disturbing ambiguity resolution. Vehicle experiments show that in GNSS-friendly scenarios, the Ambiguity Resolution (AR) success rate of the proposed model with MAQC can reach 100%, and the accuracy of attitudes are (0.12, 0.2, 0.2) degrees for heading, pitch and roll angles, respectively. Even in harsh scenarios, the AR success rate increases from about 67% for the GNSS only case to above 90% after coupling GNSS tightly with MEMS, and it is further improved to about 98% with MAQC. Meanwhile, the accuracy and continuity of attitude determination are effectively guaranteed.

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