Robotic arm

In a multiaxis, open-loop system of coupled structural members, wherein each structural member is linked for relative movement with another of the structural members to form a number of joints, an apparatus for position-calibrating each structural member with respect to one another upon receipt of a homing command, comprising

• a plurality of position sensor means, a different one of the plurality of position sensor means associated with each joint for providing a home signal when the structural members which are coupled at the corresponding joint are in a predetermined orientation, wherein a first and second structural member are connected to be relatively moveable at a joint and the position sensor means senses the position of a cable which passes along the first structural member and which drives the second structural member, and further wherein the sensor means include
• a plate pivotably connected to the first structural member and having an aperture, wherein the cable passes through the aperture and the plate is positioned to be at approximate right angles to the cable;
• cable stop means fixedly attached to the cable in the vicinity of the plate so that the cable stop means will engage the plate upon a predetermined amount of movement by the cable;
• and
• means for providing the home signal when the cable stop means and the plate engage one another;
• and
• control means responsive to the home signal from each position sensor means for modifying the position of each structural member in a predetermined order and by predetermined positional increments so that each of the structural members is caused to be positioned with respect to one another such that all position sensor means simultaneously provide home signals.

A method of position-calibrating a multiaxis, open loop system of coupled structural members, wherein each of the structural members is relatively moveable with respect to another structural member to form a number of joints and so that movement of one structural member affects the position of certain others of the structural members, and further wherein each joint includes a position sensor for providing a home signal whenever the structural members coupled at that joint achieve a predetermined home orientation with respect to one another, and wherein the position of each structural member is manipulated by a corresponding actuator means, the method comprising the steps of

• (a) commanding all actuator means to change the position of the corresponding structural member a unit step at a time until a home signal from each position sensor is received;
• (b) commanding each of the actuator means in accordance with a predetermined sequence to change the position of the corresponding structural member toward the predetermined home orientation a unit step at a time until the home signal is again received, wherein the predetermined sequence in which the actuator means are commanded begins with the actuator means corresponding to the structural member having the highest degree of coupling to the other structural members and ends with the actuator means corresponding to the structural member having the lowest degree of coupling to the other structural members;
• and
• (c) commanding each of the actuator means in accordance with the predetermined sequence to change the position of the corresponding structural member until each structural member is one unit step away from its predetermined home orientation.

In an open-loop system of structural members, wherein each structural member is linked for relative pivotable movement with another of the structural members at a different one of a plurality of joints, and further wherein at least two of the structural members are intercoupled such that the movement of one of the intercoupled structural members about a joint results in movement of the other intercoupled structural member about a different joint, an apparatus responsive to a homing command for position-calibrating the structural members with respect to a predetermined home position for each joint, comprising

• a plurality of home position means, each of which is associated with a different joint, each for providing positional information about the particular structural members coupled at the associated joint, said positional information including an indication of the direction of the predetermined home position for that joint from the current position of the particular structural members, and a home signal when the particular structural members are in the predetermined home position;
• and
• control means responsive to the home signal and to the direction indication from each home position sensor means for modifying the position of all structural members in parallel in the direction of their associated predetermined home position until all position sensing means have generated a home signal, wherein the control means reverses the direction or movement of any particular structural member whenever the associated home sensor means for the particular structural member indicates a transition from one side of its associated predetermined home position to the other, so that the position of the particular structural member is caused to vary about its associated predetermined home position until all other home position sensor means have generated a home signal and wherein the control means include means operative after all position sensing means have generated a home signal for modifying the position of each structural member, one at a time, in a predetermined order and by predetermined positional increments so that each of the structural members is caused to be moved to within a predetermined distance from its home position.

In an open-loop system of structural members, wherein each structural member is linked for relative pivotable movement with another of the structural members at a different one of a plurality of joints, and further wherein at least two of the structural members are intercoupled such that the movement of one of the intercoupled structural members about a joint results in movement of the other intercoupled structural member about a different joint, an apparatus responsive to a homing command for positioning the structural members in a home orientation, comprising

• a plurality of home position means, each of which is associated with a different joint, each for providing a first signal when the position of the particular structural members coupled at the associated joint is to one side of a predetermined home position for that joint, a second signal when the position of the particular structural members is to the other side of t he predetermined home position, and a home signal when the particular structural members are in the predetermined home position;
• and
• control means responsive to the home signal and the direction indication from each home position sensor means for modifying the position of all structural members in parallel in the direction of their associated predetermined home position until all position sensing means have generated a home signal, wherein the control means reverses the direction of movement of any particular structural member whenever the associated home sensor means for the particular structural member indicates a transition from one side of its associated predetermined home position to the other, so that the position of the particular structural member is caused to vary about its associated predetermined home position until all other home position sensor means have generated a home signal and wherein the control means include means operative after all position sensing means have generated a home signal for modifying the position of each structural member, one at a time, in a predetermined order and by predetermined positional increments so that each of the structural members is caused to be moved to within a predetermined distance from its home position.