Method and apparatus of damping the sway of the hoisting rope of a crane

A control system for damping the sway of the hoisting rope of a suspension crane comprising:

• a trolley drive control unit including:
• a traveling motor for driving the trolley of the crane, and
• a speed regulating controller which calculates a torque reference signal on the basis of a deviation signal representing a deviation of a travel speed signal representing a traveling speed of the trolley and a speed reference signal specifying a desired traveling speed of the trolley, and controls a rotating speed of the traveling motor according to the torque reference signal;
• a hoist motor for hoisting a hoist load by a hoisting rope;
• and
• a drive control unit for driving and controlling the hoist motor;
• a damping controller which determines a damping control speed correction signal (N.sub.RFDP) by using:
• N.sub.RFDP =(2.delta.g/.omega..sub.E V.sub.R)(E.THETA.) and W.sub.E =(g/L.sub.E).sup.1/2
• where E.THETA. is a swing angle of the hoisting rope, .delta. is a set damping factor, g is the gravitational acceleration constant, V.sub.R is the traveling speed of the trolley corresponding to a rated rotating speed of the traveling motor and L.sub.E is a measured length of the hoisting rope between a hoisting drive drum and the hoist load, determined on the basis of the rotating speed of the hoist motor;
• and
• a speed control means for controlling the rotating speed of the traveling motor according to a corrected speed reference signal (N.sub.RF1) obtained by subtracting the damping control speed correction signal (N.sub.RFDP) from a speed reference signal.

A method of damping the sway of a hoisting rope of a suspension crane comprising a trolley drive control unit including a traveling motor for driving a trolley;

• a hoist motor for hoisting a hoist load;
• and a hoisting motor drive control unit for driving and controlling the hoist motor;
• said method comprising the steps of:
• detecting the traveling speed of the trolley and producing a speed signal in response thereto;
• determining a torque reference signal by means of a speed regulating controller on the basis of a deviation signal representing a deviation of said speed signal from a speed reference signal;
• controlling the rotating speed of the traveling motor according to said torque reference signal;
• detecting a swing angle E.THETA. of the hoisting rope by a swing angle detector;
• calculating a damping control speed correction signal (N.sub.RFDP) by a damping controller by using:
• N.sub.RFDP ={(2.delta.g)/(.omega..sub.E V.sub.R)}(E.THETA.) and .omega..sub.E =(g/L.sub.E).sup.1/2
• where E.THETA. is the swing angle of the hoisting rope, .delta. is a set damping factor, g is the gravitational acceleration constant, V.sub.R is the traveling speed of the trolley corresponding to a rated rotating speed of the traveling motor, and L.sub.E is a length of the hoisting rope between a hoisting drive drum and the hoist load;
• and
• controlling the rotating speed of the traveling motor according to said speed reference signal obtained by subtracting said damping control speed correction signal (N.sub.RFDP) from a speed reference signal (N.sub.RF0).