Work machine control device, work machine, and work machine control method

1. A work machine control device for a work machine including a working implement with a boom, an arm, and a bucket with a blade tip, comprising:

a distance acquiring unit which acquires distance data between the bucket and a target excavating topography;

a target blade tip speed determining unit which determines a target blade tip speed of the bucket based on the distance data;

an operation amount acquiring unit which acquires an operation amount for operating the working implement;

a target boom speed calculating unit which calculates a target boom speed based on the target blade tip speed and at least one of an arm operation amount and a bucket operation amount acquired by the operation amount acquiring unit;

a correction amount calculating unit which calculates a correction amount of the target boom speed based on an integration in time of a distance between the bucket and the target excavating topography;

a correction amount limiting unit which limits the correction amount based on the distance between the bucket and the target excavating topography; and

a working implement control unit which outputs an instruction for driving a boom cylinder driving the boom based on the target boom speed corrected by the correction amount

wherein the working imlement control unit prevents the blade tip of the bucket from being raised until the blade tip of the bucket returns to the target excavating topography from the state where the blade tip digs the target excavating topography.

2. The work machine control device according to claim 1 ,

wherein the working implement control unit outputs an instruction for driving the boom cylinder to raise the boom so that a blade tip of the bucket returns to the target excavating topography from a state where the target excavating topography is dug by the blade tip of the bucket, and

wherein the correction amount limiting unit limits the correction amount in a raising operation of the boom.

3. The work machine control device according to claim 1 ,

wherein the correction amount limiting unit calculates an upper limit of the correction amount based on the distance, and

wherein the working implement control unit outputs the instruction for driving the boom cylinder based on the upper limit when the correction amount calculated by the correction amount calculating unit is larger than the upper limit calculated by the correction amount limiting unit and outputs the instruction for driving the boom cylinder based on the correction amount when the correction amount is equal to or smaller than the upper limit.

4. The work machine control device according to claim 1 ,

wherein the correction amount limiting unit decreases an upper limit of the correction amount as the distance decreases.

5. The work machine control device according to claim 1 ,

wherein the correction amount limiting unit changes an upper limit of the correction amount based on the arm operation amount or a speed of the arm.

6. The work machine control device according to claim 1 ,

wherein the correction amount limiting unit changes an upper limit of the correction amount based on a weight of the bucket.

7. The work machine control device according to claim 1 ,

wherein the correction amount limiting unit calculates an upper limit of the correction amount based on the target blade tip speed, and

wherein the upper limit decreases as the target blade tip speed decreases.

8. A work machine comprising:

a working implement which includes a boom, an arm, and a bucket with a blade tip;

a boom cylinder which drives the boom;

an arm cylinder which drives the arm;

a bucket cylinder which drives the bucket;

an upper swing body which supports the working implement;

a lower traveling body which supports the upper swing body; and

a control device,

wherein the control device includes

a distance acquiring unit which acquires distance data between the bucket and a target excavating topography,

a target blade tip speed determining unit which determines a target blade tip speed of the bucket based on the distance data,

an operation amount acquiring unit which acquires an operation amount for operating the working implement,

a target boom speed calculating unit which calculates a target boom speed based on the target blade tip speed and at least one of an arm operation amount and a bucket operation amount acquired by the operation amount acquiring unit,

a correction amount calculating unit which calculates a correction amount of the target boom speed based on an integration in time of a distance between the bucket and the target excavating topography,

a correction amount limiting unit which limits the correction amount based on the distance between the bucket and the target excavating topography, and

a working implement control unit which outputs an instruction for driving the boom cylinder based on the target boom speed corrected by the correction amount

wherein the working implement control unit prevents the blade tip of the bucket from being raised until the blade tip of the bucket returns to the target excavating topography from the state where the blade tip digs the target excavating topography.

9. A method of controlling a work machine including a working implement with a boom, an arm, a bucket with a blade tip, and a control device including a processor for performing the steps comprising:

acquiring distance data between the bucket and a target excavating topography;

determining a target blade tip speed of the bucket based on the distance data;

calculating a target boom speed based on the target blade tip speed and at least one of an arm operation amount and a bucket operation amount;

calculating a correction amount of the target boom speed based on an integration in time of a distance between the bucket and the target excavating topography;

limiting the correction amount based on the distance between the bucket and the target excavating topography;

outputting an instruction for driving a boom cylinder driving the boom based on the target boom speed corrected by the correction amount and

driving the boom cylinder based on the instruction wherein the blade tip of the bucket is prevented from being raised until the blade tip of the bucket returns to the target excavating topography from the state where the blade tip digs the target excavating topography.