In celestial mechanics, the plane of reference is the plane from which orbital elements are defined. Specifically, the inclination and the longitude of the ascending node are the two main orbital elements that are measured with respect to the plane of reference. Celestial mechanics is a division of astronomy dealing with the motions and gravitational effects of celestial objects. ... The elements of an orbit are the parameters needed to specify that orbit uniquely, given a model of two ideal masses obeying the Newtonian laws of motion and the inverse-square law of gravitational attraction. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... The Longitude of the ascending node () is one of the orbital elements used to specify the orbit of an object in space. ...
Depending on the type of body being described, there are four different kinds of reference planes that are typically used:
On the plane of reference, a zero-point must be defined from which the angles of longitude are measured. This is usually defined as the point where the plane crosses the prime hour circle on the celestial sphere (the hour circle occupied by the First Point of Aries). The plane of the Ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... The equator is an imaginary line drawn around a planet, halfway between the poles. ... The Laplace plane is defined as the mean plane occupied by the orbit of a satellite during a precession cycle. ... In astronomy and navigation, the celestial sphere is an imaginary rotating sphere of gigantic radius, concentric with the Earth. ... The First Point of Aries, also called the vernal equinox point, is one of the two points on the celestial sphere where the celestial equator intersects the ecliptic. ...
The inclinometer is placed on a plane of reference on one of the links, and generates a signal, which is a measure of the angle between the plane of reference of the link and the vertical line.
Examples of sources of error are mounting errors between the adapter plate and the plane of reference of the robot, mounting errors between the inclinometer plate and the adapter plate, and errors of tolerance of the adapter plate.
A first plane of reference on the robot is arranged on the base 1, a second plane of reference is arranged on the first arm 2, a third plane of reference is arranged on the second arm 4, and a fourth and last plane of reference is arranged on the tool attachment 6.
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