Patent ID: 8904900

Claim:
Articulated mechanical arm ( 300 ) comprising a passive device for compensation for gravity ( 150 ), which is designed to compensate for the effects of gravity on at least a first pivot connection ( 305 ) which articulates a first member ( 304 ) of the said arm on a second member ( 307 ) of the said arm, and constitutes a first degree of freedom of the said arm, characterised in that the said passive device for compensation for gravity ( 150 ) comprises a drive mechanism and at least one magnetic device, the drive mechanism being designed to transmit to the magnetic device any rotation of the second member ( 307 ) relative to the said first pivot connection, the magnetic device being designed to produce torque further to the said rotation of the second member, the drive mechanism and the magnetic device also being designed such that the said torque is retransmitted by the drive mechanism to the first pivot connection, such that the said retransmitted torque cancels the moment of force caused by the gravity which is exerted on the articulated mechanical arm, relative to the said first pivot connection, and in that the device for compensation ( 150 ) is designed to compensate for the effects of gravity on a second connection ( 306 ) which articulates the first member on the second member, and forms a second degree of freedom of the said arm, and on a third pivot connection ( 303 ) which articulates a third member of the arm ( 301 ) on the first member ( 304 ), and constitutes a third degree of freedom of the said arm, the device for compensation comprising a minimum number of magnetic devices, the said minimum number corresponding to the number of distinct sine terms which form the equations of the moment of force exerted by gravity on each of the first, second and third pivot connections once these equations are transformed to contain only sine terms, the drive mechanism being designed to transmit to each of the magnetic devices any rotation of the first, second and third members of the arm relative to the first, second and third pivot connections, the magnetic devices each being designed to produce further to these rotations a torque, the function of which is a regular sinusoid, the drive mechanism and the magnetic devices also being designed to transmit to each of the first, second and third pivot connections a corresponding counter-torque, which is the combination of the torques generated by the magnetic devices, and such that the said corresponding counter-torque cancels the moment of force caused by gravity on the first, second and third pivot connections respectively.