Gimbal Lock
Gimbal Lock (English ) or gimbal blockade called a geometric problem that can occur with transformations in conjunction with Euler angles. The term comes from English, Gimbal says here gimbalsuspended, gimbal lock is thus their blockade. Euler angle as gimbals sequentially executed corresponding to three rotations, whereby the rotation axis is also determined in each of the previous turns. The problem arises from the fact that the axis of the first rotation and may coincide with the third. Then the sum of the first and third angle is only crucial, so various combinations result in the same rotation. This lack a degree of freedom, the gimbal can not follow a movement in the corresponding direction. Is a critical value in a mathematical sense.
In practice, this is when the navigation of vessels (especially submarines and ROVs ), aviation and specifically the space of meaning, and in all applications of gimbaled gyros, mainly so in gyro compasses and stabilization gyros ( in spacecraft ).
Similar to the gimbal lock occurs even with computer models of, for example, for three-dimensional simulation, including in some computer games. A solution of the problem here is the use of quaternions represent a further solution can be done by converting the global orientations in local coordinate systems, especially when quaternions are not helpful. Inertial navigation sensors use three independent position sensors ( and three angular rate sensors ), so this problem does not occur. The data is then electronically charged.
In contrast to mathematical models, with mechanical gyro systems already an approximation to the superposition cause problems. In addition to a theoretical solution, the effect can be solved by simple servomotors in the three axes which can counteract with the risk of superposition. The countermeasures is important because two congruent mechanical axes can follow wrong with continued rotation. It is possible that both axes follow in the same orientation or continue the axes in the orientation of the respective other axis. Both cases provide a false illustrated attitude and a wrong course shown, with the result that the downstream controls respond incorrectly and thus lead to a deterioration of the situation. This rocks on in space for uncontrolled tumbling. When Gemini program was, for example, worked with a gyro compass, which had a fourth axis to the countermeasures. When compass for Apollo spacecraft was waived, the Space Shuttle, the fourth axis has been re-installed.
The Apollo Guidance Computer, which was opposite the Gemini Guidance Computer greatly improved had the display and keypad, a warning lamp for an impending gimbal lock from a changed by 70 ° axial position.