Abstract:Through the idea of equivalently transforming a free system into a constraint system,theory of mechanism can be applied to realize visualization of astronomical movement relations.An imaginary C1R2P2serial mechanism was proposed to be an equivalent system of earthsun movement system.In which,five kinematic pairs (one cylindrical pair,two rotation pairs and two movement pairs) were used to couple the earthsun movement.The meahanism was reproduced movement of any eart's location around sun by satisfying astronomy constraints such as obliquity of the ecliptic,elliptic orbit,and etc.Meanwhile,DenavitHartenberg parametric method was used to establish timespace equation of earth's location to su's center in kinematic space of the presented mechanism.The equation was applied into solar orientation,and an expression of solar direction vector by time,longitude and latitude was derivated from it.A traditional solar direction calculation was given with solar elevation angle and azimuth in Michalsky algorithm and WANG'ssolar declination formula.Finally,three examples were supplied to compare two groups of equations of solar direction,and corresponding errors were calculated.The results show that the presented mechanism and the derivated forward kinematics solar direction equation are correct.Moreover,a higher precision correction of earthsun movement can be hierarchically reproduced by adjusting or increasing movement pairs.The methodology provides a figurative means for study of astronomical kinematics,so as to better understand relationship of movement.
