Mobile body

1. A mobile body comprising:

a main body;

a drive unit configured to drive the main body;

an operating unit with which the main body is operated; and

a control unit configured to control the drive unit on the basis of an amount of operation applied to the operating unit,

wherein the operating unit includes

a pulley around which a string body is wound,

a power spring configured to urge the pulley in a direction such that the string body is wound around the pulley,

a first rotational-angle detector configured to measure an amount of rotation of the pulley,

a fixing part configured to fix the first rotational-angle detector, and

a second rotational-angle detector configured to measure an amount of rotation between the fixing part and the main body,

wherein the control unit includes

the string body that can be pulled out from and retracted with respect to the main body,

a length measurement device configured to measure a pull-out length by which the string body is pulled out, and

an angle measurement device configured to measure an angle of the string body with respect to the main body, and

wherein the control unit controls the drive unit on the basis of the results of the measurements performed by the length measurement device and the angle measurement device, and stops the drive unit if the string body is pulled out by a predetermined length or more.

2. The mobile body according to claim 1 ,

wherein the operating unit further includes

a switch that can be operated by an operator at an end of the string body, and

wherein the control unit stores a pull-out length of the string body at the time when the switch is depressed as a neutral point for a velocity of the main body.

3. The mobile body according to claim 1 , wherein the length measurement device is stored in a handle to be held by an operator.

4. The mobile body according to claim 1 , wherein the string body has elasticity.

5. The mobile body according to claim 1 ,

wherein the operating unit further includes

a guide that is fixed to the main body such that the guide is vertically swingable and that comes into contact with the string body, and

a vertical-movement detector configured to detect a vertical movement of the guide with respect to the main body, and

wherein the control unit stops controlling the drive unit and stores a pull-out length of the string body as a neutral point for a velocity of the main body when the vertical-movement detector detects the vertical movement of the guide.