Rotational joint mechanical arm gravity compensation mechanism

Abstract

The invention discloses a rotational joint mechanical arm gravity compensation mechanism, which comprises a rack, a non-circular gear planetary gear train and a plane volute spiral spring. The rack comprises a plane volute spiral spring outer end fixing rod; the non-circular gear planetary gear train comprises a tie bar, a planetary shaft, a rotary shaft, a fixed circular sun wheel, a planetary circular gear, a non-circular sun wheel and a planetary non-circular gear; the circular sun wheel is fixed onto the rack through a flange; the tie bar is connected with the planetary shaft in a sleevingway; two ends of the planetary shaft are connected with the planetary circular gear and the planetary non-circular gear; the planetary circular gear is meshed with the fixed circular sun wheel; the planetary non-circular gear is meshed with the rotary non-circular sun wheel; the rotary shaft rotates along with the non-circular sun wheel; the inner end of the plane volute spiral spring is connected with the rotary shaft through a pin; the outer end of the plane volute spiral spring is connected with a fixing rod of the rack; the tie bar is an input component; and the non-circular gear planetary gear train enables the rotary shaft to output a certain amount of turning angles, and the plane volute spiral spring is further torqued, so that an anti-balance moment is produced. The rotational joint mechanical arm gravity compensation mechanism provided by the invention is simple in structure, stable and reliable to move, high in gravity compensation precision, and applicable to a continuousrotating mechanism.

Description

technical field [0001] The invention relates to the fields of industrial robots, rehabilitation medical robots and service robots, and in particular to a gravity compensation mechanism. Background technique [0002] In the design of the robot system, for the mechanical arm whose joint axis is parallel to the ground, due to the gravity of the mechanical arm itself, additional torque will be generated at the joint, which not only reduces the dynamic characteristics of the mechanical arm to a certain extent, but also reduces the dynamic characteristics of the mechanical arm during braking. When the system fails, there is no other self-locking device, and the mechanical arm will fall under the action of gravity, seriously threatening the safety of the operator or other devices. [0003] At present, there are two existing gravity compensation methods: one is to use control means to drive the motor for active torque compensation, which requires real-time measurement of the angle o...

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Problems solved by technology

Theoretically speaking, this method can realize the complete gravity compensation of the mechanical arm, but the control algorithm is quite complicated; the second is to use the energy storage device for passive torque compensation, and drive the gravity compensation device to move through the mechanical arm joints, and the output of the gravity compensation device is opposite to the gravity moment, passive gravity compensation only needs to design the gravity compensation mechanism, and does not consume excess energy

[0004] Existing passive gravity compensation mechanisms, such as: suspension spring structure, parallel four-bar mechanism and tension spring structure, etc., cannot satisfy the nonlinear change of gravity moment, so they can only perform approximate compensation; cam tension spring structure, compensation The precision is high, but the point and line contact of the cam mechanism has relatively large wear and tear, and the cam stroke is relatively small, and the compensation range is not very large; there is a patent with the publication number CN 104245250A, which discloses the gravity of a pair of non-circular gears and tension springs. Compensation mechanism, and gravity compensation for the manipulator with high degree of freedom, the gravity moment of the manipulator whose axis of rotation joint is parallel to the ground changes according to the sinusoidal law, and the meshing of a pair of non-circular gears cannot realize the function of the precise sinusoidal law change, so Approximate Gravity Compensation

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