Patent Description:
An unmanned aerial vehicle having a winch for winding and unwinding a wire by a driving force from a driving source such as an electric motor is known in the art. This type of winch winds a wire on a spool by rotating the spool in the forward direction by driving a motor and conversely, unwinds the wire from the rotating body by rotating the spool in the backward direction. When delivering a cargo, the unmanned aerial vehicle is flown to the skies over the destination to lower the cargo attached to the wire there by unwinding the wire while hovering in the skies.

<CIT> discloses an unmanned aerial vehicle capable of transporting cargo. The unmanned aerial vehicle is provided with a winch for unwinding and winding a wire. The winding and unwinding of the winch is controlled by the operator via a transceiver or automatically according to a program as a function of an autonomous flight program.

A cargo suspended by a wire from an unmanned aerial vehicle may be lifted or lowered when the unmanned aerial vehicle is in a position that is not sufficiently visible to the operator. Therefore, it is not easy to control the winch when lifting and lowering the cargo. If the backward rotation of the spool of the winch is not properly restricted when the cargo is unloaded from the unmanned aerial vehicle that has reached the skies over the destination, the wire may become loose after the cargo is grounded, and the loose wire may become entangled with the cargo or the hook holding the cargo, or may become entangled in the winch. Further, if sufficient driving force is not applied to the spool of the winch after the cargo is unloaded, the wire unwound to the ground and the hook attached to the wire cannot be wound up to the unmanned aerial vehicle. If the unmanned aerial vehicle is flown with the wire unwound when returning from the delivery destination, the wire and the hook tend to be caught by obstacles.

In the above-mentioned Patent Literature <NUM>, winding and unwinding of the winch from the unmanned aerial vehicle is conventionally and automatically controlled only in accordance with a program, and the above-mentioned problem remains unsolved.

It is a purpose of the present invention to facilitate lifting and lowering of a cargo from an unmanned aerial vehicle. One of the more specific purposes of the present invention is to suppress loosening of a wire during unloading of a cargo from an unmanned aerial vehicle. One of even more specific purposes of the present invention is to allow the hook to be lifted to a predetermined position after unloading of a cargo. Other purposes of the invention will become apparent upon reference to this specification as a whole.

An unmanned aerial vehicle according to an embodiment of the present invention comprises: a main body; a plurality of rotary wings provided on the main body; a wire for suspending an object from the main body; a hook attached to the wire; a sensor for detecting the tension of the wire; a storage for storing a first threshold value S1 for restricting the backward rotation of the spool and a second threshold value S2 for restricting the forward rotation of the spool; a winch for rotatably supporting a spool on which the wire is wound in the forward and backward directions, winding the wire by rotating the spool in the forward direction, and unwinding the wire by rotating the spool in the backward direction; a motor for rotating the spool; and a controller for controlling the motor and configured to restricting the backward rotation of the spool when the tension of the wire becomes less than the first threshold value S1, and restricting the forward rotation of the spool when the tension of the wire becomes less than the first threshold value S1, and becomes equal to or less than the second threshold value S2 which is less than a gravitational force acting on the hook; wherein the inequality of S2 < m1 < S1 < (m1 + m2) is used to determine the first threshold value S1 and the second threshold value S2 where m1 is defined as the gravitational force acting of the hook and m2 is defined as the gravitational force acting on the cargo M.

In accordance with the present invention, the first threshold value is greater than a gravitational force acting on the hook.

In accordance with the present invention, the first threshold value is less than the sum of the gravitational forces acting on the hook and the cargo.

Embodiments of the present invention enable smooth lifting and lowering of cargo from unmanned aerial vehicles.

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings, in which:.

Hereinafter, various embodiments of the present invention will be described with reference to drawings as appropriate. The same numerical references are assigned to components common to the respective drawings. It should be noted that the drawings are not necessarily scaled for convenience of explanation.

With reference to <FIG>, an unmanned aerial vehicle <NUM> according to an embodiment of the present invention will be described. <FIG> shows a perspective view schematically indicating the unmanned aerial vehicle <NUM> according to an embodiment of the present invention, and <FIG> shows a block diagram indicating the functions of the unmanned aerial vehicle <NUM>.

As used herein, an "unmanned aerial vehicle" means an aerial vehicle that can be remotely operated, or is capable to fly autonomously, without a physical human presence within or on the aerial vehicle. The unmanned aerial vehicle <NUM> is, for example, a multicopter having a plurality of rotary wings.

As shown in <FIG>, the unmanned aerial vehicle <NUM> according to an embodiment of the present invention includes a main body <NUM>, six arms <NUM> extending outward from the main body <NUM>, six supports <NUM> provided at outer ends of the respective six arms, and six rotary wings <NUM> provided on each of the supports <NUM>. The rotary wings <NUM> are provided on the main body <NUM> via the arms <NUM> and the supports <NUM>. The unmanned aerial vehicle <NUM> may further include a winch <NUM>, a hook <NUM> and a wire <NUM>.

The support <NUM> rotatably supports the rotary wing <NUM>. The support <NUM> accommodates a drive source for providing a rotational driving force to the rotary wing <NUM>. The drive source is, for example, a motor 12a which will be described later. The rotary wing <NUM> is constructed and arranged so as to provide thrust to the unmanned aerial vehicle <NUM> during rotation.

In the illustrated embodiment, the unmanned aerial vehicle <NUM> suspends an object M with the wire <NUM>. The object M suspended from the unmanned aerial vehicle <NUM> is any object that can be suspended by the unmanned aerial vehicle <NUM>. The object M is, for example, a camera, lighting device, speaker, microphone, sensor, fire extinguishing device, a cargo and other objects.

One end of the wire <NUM> is attached to the winch <NUM>, and the other end thereof is attached to the hook <NUM>. The wire <NUM> is guided from the winch <NUM> to the hook <NUM> via a guide member provided on the lower surface of the winch <NUM>.

The wire <NUM> may be a single wire or a twisted wire made of a metal material, synthetic resin material or other materials. Suitable wire <NUM> is selected depending on the weight of the object M to be suspended, the environment of use or other factors. The wire <NUM> is desirably flexible enough to be routed from the winch <NUM> through the guide member to the hook <NUM>.

The winch <NUM> has a pair of plate-like flanges 15a and a spool 15b provided between the pair of flanges 15a. The wire <NUM> is wound on the outer peripheral surface of the spool 15b of the winch <NUM>. The spool 15b is supported by a pair of flanges 15a so as to be rotatable around a rotation axis. When the winch <NUM> is driven, the spool 15b rotates in the forward or backward direction around the rotation axis. When the spool 15b rotates in the forward direction, the wire is wound on the spool 15b. Conversely, when the spool 15b rotates in the backward direction, the wire is unwound from the spool 15b. The driving power for driving the winch <NUM> may be supplied from a battery housed in the main body <NUM>. The winch <NUM> may be unwound and wound according to a predetermined algorithm or under instructions from a remote operator.

The hook <NUM> is configured to be capable of holding the object M. The hook <NUM> may include a hook body 16a and a movable member 16b that is rotatable relative to the hook body 16a around an axis 16c. The movable member 16b can take either a closed posture in which a closed loop is made by the hook body 16a and the movable member 16b as a result of the axis 16c of the movable member <NUM> and the opposite end coming in contact with the hook body 16a, or an open posture in which the axis 16c of the movable member <NUM> and the opposite end are separated from the hook body 16a. The movable member 16b may be controlled to take a closed posture when the hook <NUM> holds a cargo M, and an open posture when the cargo M is released from the hook <NUM>. In one embodiment, the movable member 16b may maintain the closed posture when the cargo M is held by the hook <NUM> and a certain load or more is applied to the movable member 16b as shown in <FIG>, and may be automatically switched from the closed posture to the open posture when the load applied to the movable member 16b becomes less than a predetermined value or when the load applied to the movable member 16b is lost. Automatic release hooks are generally known in the art, which are configured to switch the movable member to an open posture to release a cargo when the load is detected to be less than a certain value. The automatic release hook is also referred to as a no-load release hook or an automatic cargo loading hook. Such automatic release hooks are disclosed in <CIT>, <CIT> and <CIT>. These automatic release hooks can be used as the hooks <NUM>. Instead of the automatic release hook, the hook <NUM> may be a hook which is locked to prevent the cargo M from coming off when the cargo is held, and is manually unlocked when the cargo M is unloaded. As a type of hook that is manually unlocked, for example, a carabiner hook can be used.

Next, the functions of the unmanned aerial vehicle <NUM> will be described in more detail with reference to <FIG>. As illustrated, the unmanned aerial vehicle <NUM> includes a controller <NUM>, the motor 12a for outputting a rotational driving force to the rotary wing <NUM>, a motor 12b for outputting a rotational driving force to the winch <NUM>, a sensor <NUM> and the winch <NUM>.

The controller <NUM> includes a computer processor <NUM>, a memory <NUM> and a storage <NUM>. The computer processor <NUM> is an arithmetic device that loads a flight control program defining a flight control algorithm from the storage <NUM> or other storage into the memory <NUM>, and executes instructions contained in the loaded flight control program. In addition to the flight control program, the computer processor <NUM> can execute various programs related to the realization of the functions of the unmanned aerial vehicle <NUM>. The controller <NUM> may be configured to control the rotational speed of the motor 12a and the motor 12b by outputting a PWM signal to the motor 12a and the motor 12b.

In accordance with the invention, the sensor <NUM> is a tension sensor that detects tension on the wire <NUM>. For example, a strain gauge may be used as the sensor <NUM>. In addition to the sensor <NUM>, the unmanned aerial vehicle <NUM> may include a gyro sensor, acceleration sensor, geomagnetic sensor, barometric pressure sensor and various other sensors. These sensors are connected to the controller <NUM> as necessary.

The controller <NUM>, the motor 12b, the sensor <NUM>, a communication device and a battery may be accommodated in the main body <NUM>. In addition to the illustrated components, the unmanned aerial vehicle <NUM> may include communication devices, batteries and various other devices necessary for its own operation. These components are connected to the controller <NUM> as necessary.

The controller <NUM> may be configured to control the attitude and position of the unmanned aerial vehicle <NUM> by controlling the rotational speed of the rotary wing <NUM> according to a flight control algorithm based on detection information of various sensors provided in the unmanned aerial vehicle <NUM>.

The storage <NUM> stores a first threshold value S1 for restricting the backward rotation of the spool 15b and a second threshold value S2 for restricting the forward rotation of the spool 15b. The controller <NUM> can restrict the rotation of the spool 15b, comparing the tension of the wire <NUM> detected by the sensor <NUM> with the first and the second threshold values. In one embodiment, the controller <NUM> controls the rotation of the motor 12b so that the spool 15b does not rotate in the backward direction when the tension of the wire <NUM> is less than or equal to the first threshold value. As a result, when the tension of the wire <NUM> is equal to or less than the first threshold value, the wire <NUM> is not unwound. Conversely, when the tension of the wire <NUM> is greater than the first threshold value, the controller <NUM> may drive the motor 12b such that the spool 15b rotates in the backward direction. In accordance with the invention, the first threshold value S1 is supposed to be greater than the gravitational force m1 acting on the hook <NUM>, that is, m1<S1. In addition, the first threshold value is supposed to be less than the sum (m1+m2) of the gravitational force m1 acting on the hook <NUM> and the gravitational force m2 acting on the cargo M to be transported, that is, S1 < (m1+m2. ) The inequality m1 < S1 < (m1+m2) is used. The first threshold value S1 and the second threshold value S2 may be changed by an operator of the unmanned aerial vehicle <NUM> or an operator involved in the transportation of the cargo M. For example, when instead of the hook <NUM>, another hook is attached to the wire <NUM>, the values of the first threshold value S1 and/or the second threshold value S2 may be changed according to the weight of the new hook. Further, the first threshold value S1 may be changed according to the weight of the cargo M to be transported.

In one embodiment, the controller <NUM> controls the rotation of the motor 12b so that the spool 15b does not rotate in the forward direction when the tension of the wire <NUM> is equal to or less than the second threshold value. As a result, when the tension of the wire <NUM> is equal to or less than the second threshold value, the wire <NUM> is not wound. Conversely, when the tension applied to the wire <NUM> is greater than the second threshold value, the controller <NUM> can drive the motor 12b so that the spool 15b rotates in the forward direction. In one embodiment, the second threshold value is supposed to be less than the first threshold value and less than the gravitational force m1 acting on the hook <NUM>.

Next, with reference to <FIG>, a method of unloading the cargo M from the unmanned aerial vehicle <NUM> will be described. In <FIG>, it is assumed that the unmanned aerial vehicle <NUM> carrying the cargo M has reached the skies over the destination to unload the cargo M there.

When the unmanned aerial vehicle <NUM> reaches the skies over the destination, first, as shown in <FIG>, the rotation of the motor 12b is controlled to rotate the spool 15b in the backward direction, and the wire <NUM> is unwound from the spool 15b. Since the cargo M is held by the wire <NUM> via the hook <NUM>, the cargo M can be lowered from the sky toward the ground by unwinding the wire <NUM>. The backward rotation of the spool 15b may be controlled under instructions from the operator, or may be controlled automatically on the basis of the control of the controller <NUM> when detecting that the spool 15b has reached the skies over the destination (not under instructions from the operator. ) The backward rotation of the motor 12b is prohibited when the tension T of the wire <NUM> is equal to or less than the first threshold value S1. When the cargo M is lowered from the sky toward the ground G, the tension T exerted on the wire <NUM> is equal to (m1+m2) or greater than (m1+m2) by the gravitational force exerted on the wire <NUM>, that is, (m1+m2) ≦ T holds. Therefore, by making the first threshold value S1 less than the total gravitational forces (m1+m2) of the hook <NUM> and the cargo M (namely, by letting S1 < (m1+m2,)) the tension T acting on the wire <NUM> becomes greater than the first threshold value S1 (S1<T. ) Accordingly, the backward rotation of the spool 15b is not restricted while the cargo M is lowered from the sky toward the ground G. Therefore, the cargo M can be smoothly lowered from the sky to the ground G.

As the wire <NUM> continues to be unwound, the cargo M reaches the ground G as shown in <FIG>. When the cargo M reaches the ground G, the tension T exerted on the wire <NUM> changes. More specifically, since the cargo M is supported upward by the ground G, the tension T exerted on the wire <NUM> becomes smaller than before the cargo M reaches the ground G. When the cargo M reaches the ground G, the cargo M is released from the hook <NUM> by manipulation of an operator on the ground G as shown in <FIG>, or automatically if the hook <NUM> is an automatic release hook. When the cargo M is released from the hook <NUM>, the tension T of the wire <NUM> becomes substantially equal to the gravitational force m1 acting on the hook <NUM>, that is, T ≈ m1 holds. Therefore, by making the first threshold value S1 greater than the gravitational force m1 acting on the hook <NUM> (namely, by letting m1 < S1,) the tension T acting on the wire <NUM> becomes less than the first threshold value S1 (T<S1,) and therefore, after the cargo M is released from the hook <NUM>, the wire <NUM> is not further unwound. It is thus possible to prevent the wire <NUM> from loosening when the cargo M is released.

As described above, when the cargo M is released from the hook <NUM>, the tension T acting on the wire <NUM> becomes substantially equal to m1, so that the controller <NUM> can detect that the cargo M is released from the hook <NUM> based on the detection signal from the sensor <NUM>. For example, the controller <NUM> can determine that the cargo M has been released from the hook <NUM> when the tension detected by the sensor <NUM> becomes less than a predetermined threshold value. The controller <NUM> may drive the motor 12b in the forward direction when determining that the cargo M has been released from the hook <NUM>. The hook <NUM> from which the cargo M is released can be retrieved by driving the motor 12b in the forward direction after the cargo M is released. For example, as shown in <FIG>, after the cargo M is released from the hook <NUM>, the wire <NUM> is wound onto the spool 15b. The wire <NUM> may be wound up until the hook <NUM> rises to a position where the flight of the unmanned aerial vehicle <NUM> is not hindered. When winding the wire <NUM> after release of the cargo M, the tension T exerted on the wire <NUM> becomes substantially equal to the gravitational force m1 acting on the hook <NUM> as described above. Therefore, by making the second threshold value S2 less than the gravitational force m1 acting on the hook <NUM> (namely, by letting S2 < m1,) the tension T acting on the wire <NUM> becomes greater than the second threshold value S2 (S2 < T,) so that the forward rotation of the spool 15b is not restricted during the winding of the wire <NUM> after the release of the cargo M. As a result, the wire <NUM> can be smoothly wound up until the hook <NUM> rises to a predetermined position.

Next, the effect of the above embodiment will be described. In the above-described embodiment, under the control of the controller <NUM>, when the tension T of the wire <NUM> becomes equal to or less than the first threshold value S1, the backward rotation of the spool 15b is restricted (i.e., the backward rotation is prohibited,) and when the tension T becomes equal to or less than the second threshold value S2, the forward rotation of the spool 15b is restricted (i.e., the forward rotation is prohibited. ) The second threshold value S2 is less than the first threshold value S1 and the gravitational force m1 acting on the hook <NUM>, respectively. When winding the wire <NUM> after releasing the cargo M from the hook <NUM>, the tension T of the wire <NUM> becomes substantially equal to the gravitational force m1 acting on the hook <NUM>. In this manner, by making the second threshold value S2 for restricting the forward rotation less than the gravitational force m1 acting on the hook <NUM>, the winding of the wire <NUM> after the release of the cargo M can be smoothly performed without restricting the forward rotation of the spool 15b. If the second threshold value S2 is set to a value equal to or greater than the gravitational force m1 acting on the hook <NUM>, the tension T acting on the wire <NUM> after the release of the cargo M is the gravitational force m1 acting on the hook <NUM>, so that the tension T becomes less than the second threshold value S2, which restricts the winding of the spool 15b. Therefore, if the second threshold value S2 is set to a value equal to or greater than the gravitational force m1 acting on the hook <NUM>, the wire <NUM> cannot be retrieved. On the other hand, as in the above embodiment, the wire <NUM> can be retrieved by making the second threshold value S2 less than the gravitational force m1 acting on the hook <NUM>.

In the above embodiment, the first threshold value S1 is greater than the gravitational force m1 acting on the hook <NUM>. Thus, after the release of the cargo M from the hook <NUM>, the tension T acting on the wire <NUM> can be made less than the first threshold value S1. Therefore, after the release of the cargo M from the hook <NUM>, unnecessary unwinding of the wire <NUM> can be prevented by prohibiting the backward rotation of the spool 15b. This can prevent the wire <NUM> from loosening when the cargo M is released. If the first threshold value S1 is set to a value less than the gravitational force m1 acting on the hook <NUM>, the wire <NUM> continues to be unwound as the backward rotation of the spool 15b is not restricted even after the cargo M is grounded. Therefore, if the first threshold value S1 is set to a value less than the gravitational force m1 acting on the hook <NUM>, the amount of the wire <NUM> unwound after the cargo M is grounded becomes greater than that in the embodiment of the present invention in which the first threshold value S1 is set to a value greater than the gravitational force m1 acting on the hook <NUM>, which makes the line become easier to slack off.

In accordance with the invention, the first threshold value S1 is less than the sum of the gravitational force m1 acting on the hook <NUM> and the gravitational force m2 acting on the cargo M. As a result, the tension T acting on the wire <NUM> can be made greater than the first threshold value S1 when the cargo M is descended from the sky toward the ground G, so that the cargo M can be smoothly descended to the ground G without restricting the backward rotation of the spool 15b.

The dimensions, materials and arrangements of each component described herein are not limited to those explicitly described in the embodiments, and each component can be modified to have any dimension, material and arrangement that can be included within the scope of the present invention which is defined by the appended claim.

Claim 1:
An unmanned aerial vehicle (<NUM>) comprising:
a main body (<NUM>);
a plurality of rotary wings (<NUM>) provided on the main body;
a wire (<NUM>) for suspending an object from the main body;
a hook (<NUM>) attached to the wire (<NUM>);
a sensor (<NUM>) for detecting the tension of the wire (<NUM>);
a winch (<NUM>) for rotatably supporting a spool (15b) on which the wire is wound in the forward and backward directions, winding the wire (<NUM>) by rotating the spool (15b) in the forward direction and unwinding the wire (<NUM>) by rotating the spool (15b) in the backward direction;
a motor (12b) for rotating the spool (15b);
storage (<NUM>) for storing a first threshold value S1 for restricting the backward rotation of the spool and a second threshold value S2 for restricting the forward rotation of the spool;
and
a controller (<NUM>) configured to control the motor (12b) and restrict the backward rotation of the spool (15b) when the tension of the wire (<NUM>) becomes less than the first threshold value S1;
characterized in that the controller (<NUM>) is further configured to (i) determine whether a cargo (M) has been released from the hook (<NUM>) and then drive the motor (12b) in the forward direction when determining that the cargo (M) has been released from the hook (<NUM>), and (ii) when winding the wire (<NUM>) after release of the cargo (M), restrict the forward rotation of the spool (15b) when the tension of the wire (<NUM>) becomes less than the first threshold value S1 and becomes equal to or less than the second threshold value S2, which is less than a gravitational force acting on the hook (<NUM>);
wherein the inequality of S2 < m1 < S1 < (m1 + m2) is used to determine the first threshold value S1 and the second threshold value S2 where m1 is defined as the gravitational force acting on the hook and m2 is defined as the gravitational force acting on the cargo (M).