# US 5,241,249 A · Process for controlling a robot arm by defining substitution paths > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,241,249 A - Document ID: US5241249A - Status: Granted - Kind: A - Application number: 07/817,770 - Filed: 1992-01-08 - Granted: 1993-08-31 - Earliest claimed: 1991-01-09 - Assignees: Commissariat a l'Energie Atomique - Inventors: Jean-Marie Detriche - Web page: https://patentgrep.com/patent/US5241249A ## CPC - B25J 9/1664: {characterised by motion, path, trajectory planning} - B25J 9/1679: {characterised by the tasks executed} - G05B 2219/40521: Alternative, allowable path substitution if arm movements not possible - B25J: MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES ({manipulators specially adapted for use in surgery A61B34/70; manipulators used in cleaning hollow articles B08B9/04}; manipulators associated with rolling mills B21B39/20; manipulators associated with forging machines B21J13/10; {manipulators associated with picking-up and placing mechanisms B23P19/007}; means for holding wheels or parts thereof B60B30/00; {vehicles with ground-engaging propulsion means, e.g. walking members B62D57/02, B62D57/032; devices for picking-up and depositing articles or materials between conveyors B65G47/90, B65G47/91; manipulators with gripping or holding means for transferring packages B65H67/065}; cranes B66C; {manipulators used in the protection or supervision of pipe-line installations F17D5/00; walking equipment adapted for nuclear steam-generators F22B37/006}; manipulators specially adapted for, or associated with, nuclear reactors G21C; {apparatus used for handling wafers during manufacture or treatment of semiconductor H10P72/50}) - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) ## Abstract A process for controlling a robot arm having a certain number of articulations or joints (A to F), which can abut. Substitution paths are automatically defined by calculation or by the choice of intermediate objectives in order to arrive at destination points, when the direct path would involve the abutment of certain joints. ## Claims ### Claim 1 A process for controlling a robot arm in moving a wrist at an end of the arm to an objective, the arm comprising rigid sections connected by joints, the sections taking relative positions at the joints which correspond to joint states, the joint states having allowed ranges limited to abutment states, comprising the automatic steps of: defining a direct path from a current wrist position to the objective; computing sets of theoretical joint states for the robot arm to carry the wrist along the direct path when the joints together take the joint states of each set successively; updating all sets that comprise at least one theoretical joint state outside the allowed range of joint states to create updated sets in which all the joint states are within the allowed ranges; discarding the sets that comprise at least one theoretical joint state outside the allowed range of joint states; and moving the wrist along a substitution path by bringing the joints through the computed sets of theoretical joint states that comprise no joint state outside the allowed range of joint states and the updated sets. ### Claim 2 (depends on 1) A process according to claim 1, wherein the updated sets are created by replacing the theoretical joint states outside the allowed ranges with joint states within the allowed ranges. ### Claim 3 (depends on 1) A process according to claim 1, wherein the joint states within the allowed ranges are abutment states. ### Claim 4 (depends on 1) A process according to claim 1, wherein the substitution path is interrupted when at least one of the joints reaches a theoretical joint state outside the allowed range of joint states. ### Claim 5 (depends on 1) A process according to claim 1, wherein the substitution path is interrupted when a selected number of the joints reach a theoretical joint state outside the allowed range. ### Claim 6 A process for controlling a robot arm in moving a wrist at an end of the arm to an objective, the arm comprising rigid sections connected by joints, the sections taking relative positions at the joints which correspond to joint states, the joint states having allowed ranges limited by abutment states, comprising the automatic steps of: defining a direct path from a current wrist position to the objective; computing sets of theoretical joint states for the robot arm to carry the wrist along the direct path when the joints together take the joint states of each set successively; discarding the sets that comprise at least one theoretical joint state outside its allowed range; and moving the wrist along a substitution path by bringing the joints through the computed sets of theoretical joint states that comprise no joint state outside the allowed range of joint states. ### Claim 7 (depends on 6) A process according to claim 6, wherein all the sets of theoretical joint states that the joints should take after at least one of the sets that comprise at least one theoretical joint state outside an allowed range are discarded. ### Claim 8 (depends on 6) A process according to claim 6, wherein the substitution path is interrupted when at least one of the joints reaches a theoretical joint state outside the allowed range of joint states. ### Claim 9 (depends on 6) A process according to claim 6, wherein the substitution path is interrupted when a selected number of the joints reach theoretical a joint state outside the allowed range. ### Claim 10 (depends on 6) A robot arm control process according to claim 6, characterized in that the arm has three sections (2,3,4) articulated for rotation in a horizontal plane and jointly mobile in vertical translation, a fourth section (7) articulated for rotation a plane vertical to one of the three preceding sections and a member (8) articulated to the fourth section for rotation in accordance with a pivoting movement.