Te in the local horizontal geographic frame and that inside the grid frame is deduced. Flight experiments at mid-latitudes initially proved the effectiveness of the covariance transformation system. It truly is tough to conduct experiments within the polar area. A purely mathematical simulation can’t accurately reflect true aircraft conditions [19]. To solve this trouble, the authors of [19,20] proposed a virtual polar-region approach primarily based around the t-frame or the G-frame. In this way, the experimental information from middle and low latitude regions is usually converted to the polar area. Verification by semi-physical simulations, primarily based on the proposed approach by [20], can also be conducted and offers far more convincing results. This paper is organized as follows. Section two describes the grid-based strap-down inertial navigation method (SINS), including the mechanization and dynamic model with the grid SINS. In Section 3, the covariance transformation system is presented. Also, Section 3 also presents a navigation frame-switching method primarily based on the INS/GNSS integrated navigation technique. Section four verifies the effectiveness of the proposed strategy via experimentation and semi-physical simulation. Finally, common conclusions are discussed in Section five. 2. The Grid SINS two.1. Grid Frame and Grid SINS Mechanization The definition from the grid reference frame is shown in Figure 1. The grid plane is parallel towards the Greenwich meridian, and its intersection together with the tangent plane in the position in the aircraft may be the grid’s north. The angle between geographic north and grid north gives the grid angle, and its clockwise path could be the optimistic direction. The upAppl. Sci. 2021, 11,Appl. Sci. 2021, 11,3 of3 ofnorth offers the grid angle, and its clockwise direction may be the constructive path. The up direction with the grid frame is definitely the similar as that from the nearby geographic frame and forms an direction with the grid frame is definitely the similar as that on the local geographic frame orthogonal right-handed frame with the orientations at grid east and grid north. and types an orthogonal right-handed frame with the orientations at grid east and grid north.Figure 1. The definition from the grid reference frame. The blue arrows Iodixanol Technical Information represent the 3 coordinate Figure 1. The the nearby geographic frame. The orange arrowsarrows represent thecoordinate axes of the axes of definition in the grid reference frame. The blue represent the 3 3 coordinateframe. the nearby geographic frame. The orange arrows represent the 3 coordinate grid axes of axes with the grid frame.The grid angle is expressed as alpha-D-glucose Protocol discovered in [9]: The grid angle is expressed as identified in [9]: sin = sin L sinsin =1sin sin L -cos2 L sin2 cos – cos 2 Lcos = sin two(1)cos CG The direction cosine matrix e= between2the G-frame along with the e-frame (earth frame) is 1 – cos L sin 2 as discovered in [9]: G G G Ce = Cn Cn e The direction cosine matrix C among the G-frame and also the e-frame (earth frame) (two)ecos1-cos2 L sin(1)G where n [9]: is as identified in refers for the neighborhood horizontal geographic frame. Cn and Cn are expressed as: e G G n (two) -C e C n C e cos sin = 0 Cn = – sin L cos – sin L sin cos L e n G where n refers towards the neighborhood horizontalcos L cos frame. sin and C n are expressed as: geographic cos L C e sin L(three)- – sin cos cos sin 0 0 G – sinCn cos sin L sin 0cos L n = – sin cos (four) Ce = L (3) 0 0 1 cosL cos cos L sin sin L The updated equations from the attitude, the velocity, along with the position in th.
