Patent ID: 8369993

Claim:
A method of positionally calibrating a tip of an arm of a manipulated type of robot by using a computer, the arm tip being defined as a tip of a tool held by the arm, comprising steps of: calculating with the computer, at a plurality of positions at which the arm tip is moved, n pieces of errors (Δφ: Δφ 1 , Δφ 2 , . . . , Δφ n , wherein n is a natural number larger than a value obtained by dividing the number of unknown parameters by 6), respectively, each of the errors being an error between a position of the arm tip measured by a measurement device and a position commanded by control at each of the plurality of positions; calculating an inter-error difference (Δε y (1≦y≦n−1)) between a given reference error (Δφ m (1≦m≦n)) arbitrarily selected from the n-piece errors (Δφ) and other errors (Δφ x (x≦n, except for m)) left other than the given reference error (Δφ m ) among the n-piece errors; and making a parameter, which is a basis for calculating the inter-error differences (Δε y ), converge until a sum of absolute values of the respective inter-error differences (Δε y ) becomes equal to or less than a given threshold (ε 0 (ε 0 >0)), wherein the converging step further includes steps of: calculating a Jacobian determinant (J) for parameter matrices (q, θ), wherein (q) is a matrix of the parameters arid θ is a matrix of angles of respective axes of the arm, calculating an error matrix (Δq) of the parameter matrix q based on a product of an inter-error difference (Δε y ) and a simulated inverse matrix of the Jacobian determinant (J), updating the parameter matrix (q) by adding the error matrix (Δq) to the parameter matrix (q), and re-calculating the position of the arm tip depending on the updated parameter matrix (q), so that the parameter matrix (q) is made to converge so as to calibrate the position of the arm tip.