Robot joint angle detecting system

Claim 2

A robot joint angle detecting system for detecting a rotational angle of a joint (2) coupled through a reduction mechanism (3) to a drive motor (M) for driving the joint, an absolute-type rotational angle detector (RE) coupled to the shaft of the motor for detecting the rotational angle of the motor, an incremental-type rotation number detector (PG, 4) coupled to the shaft of the motor for detecting the rotation number of the motor, and means (7) responsive to the detected rotational angle of the motor and the detected rotation number of the motor for determining the rotational angle of the joint, characterized in that said incremental-type rotation number detector is provided with a battery (9) for energization during interruption of a power supply.

Claim 3

A system of claim 1, wherein the robot is provided with a plurality of joints (2), and a combination of said motor (M), said absolute-type rotational angle detector (RE), and said incremental-type rotation number detector (PG, 4) is provided for each of the joint (2), and said battery (9) is provided exclusively for the incremental-type rotation number detector of the individual combination.

Claim 4

A system of claim 2, wherein said combination form a unit (18) which can be readily separated from the rest of the system.

Claim 5

A system of claim 1, wherein said incremental-type rotation number detector (PG, 4) comprises a pulse generator (PG) producing pulses in synchronism with rotation of the motor and a counter (4) counting the pulses from the pulse generator for producing a count value signal indicative of the rotation number.

Claim 6

A system of claim 4, further comprising a latch circuit (5) latching the count value signal from the counter, wherein said determining means (7) determines the joint angle from the output of the latch circuit (5) and the output of the absolute-type rotational angle detector (RE).

Claim 7

A system of claim 5, further comprising a transmitting unit (19) built in the main body of the robot, wherein said latch circuit (5) is also built in the main body of the robot said determining means (7) is built in a robot controller unit (20), and the output of said latch circuit (5) is transmitted through said transmitting unit (19) to said determining means.

Claim 8

A system of claim 1, wherein said incremental-type rotation number detector (PG, 4) comprises a disk (103;113), two sets of photocouplers (104A, 104B) positioned 90° apart from each other along the periphery of the disk, a drive circuit (102) for feeding drive pulses to the photocouplers, a pair of latch circuits (105A, 105B) respectively latching the outputs of the photocouplers, a direction discriminator (106) responsive to the outputs of the photocouplers for discriminating between the directions of rotation of the motor, and an up-down counter (4) counting up or down depending on the result of the discrimination.

Claim 9

A system of claim 1, further comprising means (141, 143) responsive to the output of the rotation angle detector (RE) and the output of the rotation number detector (PG, 4) for effecting zero position correction for the rotation number detector.

Claim 10

A system of claim 8, wherein the rotation number detector (PG, 4) and the rotational angle detector (RE) are so aligned that the rotation number detected value of the rotation number detector varies by 1 when the rotation angle of the rotational angle detector is substantially at 0°, said system further comprising means (4) for producing a logic signal which varies from a first level to a second level when the rotation number detected value varies by 1 and which varies from the second level to the first level at a time point between the time points when the rotation number detected value varies by 1, means (141) for producing a plus correction signal when the rotational angle detected value is larger than a first predetermined value close to 360° and said logic signal is at said second level, and producing a minus correction signal when the rotational angle detected value is smaller than a second predetermined value close to 0° and said logic signal is at said first level, and means (143) adding 1 to said rotation number detected value when the plus correction signal is produced and subtracting 1 from said rotation number detected value when the minus correction signal is produced, thereby to produce a corrected detected value of the rotation number.

Claim 11

A system of claim 9, wherein said rotation number detection (PG, 4) comprises means (106) producing pulses twice per rotation and a counter (4) counting the pulses from said pulse producing means (106), wherein the outputs of the counter (4) except the least significant bit are produced as the rotation number detected value while the least significant bit is used as said logic signal.