Method for controlling the operation of power excavator

A method for controlling the operation of a power excavator during a land finishing work, the excavator having handling signal input means, a boom, an arm, a bucket and a swing unit, and a plurality of angular displacement sensors comprising a boom sensor, an arm sensor and a bucket sensor, the method comprising the steps of:

• a) initializing start and end point coordinates of a bucket tip, positioned on land finishing start and end points, and initializing an object land finishing angle, and setting on a flag in order to store the start point coordinate during an automatic land finishing work;
• b) receiving boom angle data from the boom sensor, arm angle data from the arm sensor, bucket angle data from the bucket sensor and operator's handling signal data output from the handling signal input means, said operator's handling signal data comprising arm handling signal data, bucket handling signal data and swing unit handling signal data;
• c) checking whether the direction of said arm handling signal of step (b) has been changed;
• d) when said arm handling signal has been changed, checking whether said flag has been set off;
• e) when said flag has been set on, performing a predetermined geometric operation of the boom angle data, arm angle data and bucket angle data, thus calculating the end point coordinate of the bucket tip prior to calculating the object land finishing angle using said start and end point coordinates;
• f) when said flag has been set off, performing a predetermined geometric operation of the boom angle data, arm angle data and bucket angle data, thus calculating the end point coordinate of the bucket tip prior to setting on the flag;
• g) checking whether said boom handling signal has been output from said handling signal input means;
• h) when said boom handling signal has been output from the handling signal input means, performing a predetermined operation of the data of the boom handling signal in order to generate a manual boom control signal for controlling the boom in response to said boom handling signal;
• i) when said boom handling signal has not been output from the handling signal input means, performing a predetermined geometric operation of the boom angle data, arm angle data, bucket angle data and land finishing angle, thus calculating reference boom angle data used as reference data for controlling the boom in order to move the bucket tip on the land with the land finishing angle in response to said arm handling signal output from said handling signal input means;
• j) comparing said reference boom angle data with the boom angle data, thus calculating a difference (error data) between the two angle data;
• k) performing a predetermined control operation of said error data, thus generating an automatic boom control signal;
• l) performing an operation of either said manual control signal of step (h) or said automatic control signal of step (k) in order to generate a current control signal for the boom, and performing an operation of the arm handling signal data, bucket handling signal data and swing unit handling signal data of step (b) in order to generate current control signals for the arm, bucket and swing unit, and outputting said current control signals to directional control valves associated with the boom, bucket, arm and swing unit;
• and
• m) returning to step (b) in order to repeat steps (b) to (l).

A control system for automatically controlling a working implement of a power excavator, said working implement including a boom, an arm, a bucket and a swing unit, and said power excavator further comprising handling signal input means handled by an operator and a plurality of sensing means for detecting angular displacement of said boom, arm and bucket, wherein said control system comprises:

• means for detecting a change in a motional direction of said arm, said change being made by an arm handling signal output from said handling signal input means;
• means for computing an object operational angle of said bucket by performing a predetermined geometrical calculation based on said positional signals detected at a plurality of points where the motional direction of said arm is changed;
• and
• means for controlling said boom in accordance with either one of the following manners by a predetermined operation based on handling signals output from said handling signal input means and positional signals output from said sensing means, wherein:
• when an operator controls said boom, said boom is controlled in response to a boom handling signal output from said handling signal input means;
• when the operator controls said arm and does not control said boom, said boom is controlled so that an end of said bucket moves at said object operational angle in response to said arm handling signal output from said handling signal input means.