A work machine provided with a lifting magnet includes the lifting magnet, an arm that supports the lifting magnet, a boom that supports the arm, an upper turning body that supports the boom, an engine, a selective catalytic reduction system, and a controller that controls attraction and release by the lifting magnet.

A work machine provided with a lifting magnet includes the lifting magnet, an arm that supports the lifting magnet, a boom that supports the arm, an upper turning body that supports the boom, an engine, a selective catalytic reduction system, and a controller that controls attraction and release by the lifting magnet.

A method for using a lifting magnet and a lifting magnet. The lifting magnet includes a plurality of electromagnet coils that are each independently ON/OFF-controllable and voltage-controllable, and a magnetic pole that is excited by application of a voltage to the electromagnet coils. An electromagnet coil to be used for lifting steel plates is determined based on a total thickness of the steel plates to be lifted. An amount of passing magnetic flux ?.sub.r in the magnetic pole in a case where magnetic flux passes through only the steel plates to be lifted when the electromagnet coil is used is calculated. An application voltage to be applied to the electromagnet coil used for lifting the steel plates is determined based on the amount of passing magnetic flux ?.sub.r. The application voltage is applied to the electromagnet coil.

A method for using a lifting magnet and a lifting magnet. The lifting magnet includes a plurality of electromagnet coils that are each independently ON/OFF-controllable and voltage-controllable, and a magnetic pole that is excited by application of a voltage to the electromagnet coils. An electromagnet coil to be used for lifting steel plates is determined based on a total thickness of the steel plates to be lifted. An amount of passing magnetic flux ?.sub.r in the magnetic pole in a case where magnetic flux passes through only the steel plates to be lifted when the electromagnet coil is used is calculated. An application voltage to be applied to the electromagnet coil used for lifting the steel plates is determined based on the amount of passing magnetic flux ?.sub.r. The application voltage is applied to the electromagnet coil.

When at least one of a value a detected output current to a magnet and a magnet load defined by the following formula (1) is equal to or larger than a threshold value predetermined for the value of the detected output current or a threshold value predetermined for the magnet load, a controller constituting a control device outputs, to a control circuit, a command to decrease voltage applied to the magnet from next attracting operation. Magnet load=excitation ratioIV . . . (1); in which excitation ratio: excitation time/(excitation time+non-excitation time); I: value of the output current; V: voltage applied to a lifting magnet.

When at least one of a value a detected output current to a magnet and a magnet load defined by the following formula (1) is equal to or larger than a threshold value predetermined for the value of the detected output current or a threshold value predetermined for the magnet load, a controller constituting a control device outputs, to a control circuit, a command to decrease voltage applied to the magnet from next attracting operation. Magnet load=excitation ratioIV . . . (1); in which excitation ratio: excitation time/(excitation time+non-excitation time); I: value of the output current; V: voltage applied to a lifting magnet.

An unmanned aerial vehicle according to an embodiment of the present invention includes: an aerial vehicle body capable of flying; a winding member provided to the aerial vehicle body and capable of winding and unwinding a linear member; an attractive member provided to an end portion of the linear member and configured to generate a magnetic attraction force between the attractive member and an attraction-responsive part that is ferromagnetic and provided to a delivery target; and a holding mechanism configured to hold the delivery target T in a state in which the attractive member and the attraction-responsive part are coupled to each other by the magnetic attraction force.

An unmanned aerial vehicle according to an embodiment of the present invention includes: an aerial vehicle body capable of flying; a winding member provided to the aerial vehicle body and capable of winding and unwinding a linear member; an attractive member provided to an end portion of the linear member and configured to generate a magnetic attraction force between the attractive member and an attraction-responsive part that is ferromagnetic and provided to a delivery target; and a holding mechanism configured to hold the delivery target T in a state in which the attractive member and the attraction-responsive part are coupled to each other by the magnetic attraction force.

Simplification of a device configuration and control is realized, which enables attraction and release by a magnet without using a battery. A magnet work machine includes a generator motor (8) driven by an engine (7); and an inverter (10) which controls a magnet (6) and the generator motor (8) such that the magnet (6) is energized by electric power from the generator motor (8) to attract metal scraps or the like, and during demagnetization for releasing metal scraps or the like, electric power applied to the magnet (6) is transmitted to the generator motor (8) as regenerative power so as to be consumed. The inverter (10) determines a torque of the generator motor (8) as a motor according to a voltage change of a main circuit based on a detected main circuit voltage so as to suppress the voltage change, and gives the torque as a command.

Simplification of a device configuration and control is realized, which enables attraction and release by a magnet without using a battery. A magnet work machine includes a generator motor (8) driven by an engine (7); and an inverter (10) which controls a magnet (6) and the generator motor (8) such that the magnet (6) is energized by electric power from the generator motor (8) to attract metal scraps or the like, and during demagnetization for releasing metal scraps or the like, electric power applied to the magnet (6) is transmitted to the generator motor (8) as regenerative power so as to be consumed. The inverter (10) determines a torque of the generator motor (8) as a motor according to a voltage change of a main circuit based on a detected main circuit voltage so as to suppress the voltage change, and gives the torque as a command.