The invention relates to a low-speed non-throwing control method for sewing cloth by a
sewing machine, a needle and a take-up lever of the
sewing machine are driven by a main shaft, and the method comprises the following steps: S1, determining a non-throwing safe aperture D1; determining the time tD required from the time when the
machine needle upwards leaves the cloth to the time when the needle eye hole shrinks to the non-throwing thread safe aperture D1; s2, recording AT / T =
omega n; in one operation cycle, determining an angle A1 corresponding to the main shaft when a
machine needle upwards leaves the cloth, and determining an angle A2 corresponding to the main shaft when the take-up lever finishes the take-up action; s3, setting a function
omega = f (A) of the
angular velocity of the main shaft with respect to the angle of the main shaft in one operation cycle, and satisfying the following conditions: f (0) = f (AT), f (A) is continuously derivable, and f '(0) = f' (AT); in the interval of 0-A1,
omega is increased to omega n and continues to be increased; when t1 = A1 / omega n, the angle of the main shaft is A1; the time t2 for rotating to A2 meets the condition that t2-t1 < = tD; the main shaft angle is AT at the time T; and S4, in one operation cycle, the angle of the main shaft is obtained in real time, and the main shaft is controlled to rotate through the function relation omega = f (A).