Mobile wheeled device with drive wheels

Abstract

A mobile wheeled device, such as a hospital bed, comprises a base having a plurality of non-driven wheels and one wheel driven by an electric motor (51), a sensor arrangement (65) for detecting a signal indicative of a force acting on the mobile wheeled device, and a controller (64) configured to drive the electric motor (51) in dependence on the signal detected by the sensor arrangement (65). The electric motor is contained in the hub of the driven wheel. The sensor arrangement is arranged at the driven wheel and comprises a rotary encoder (56, 59) located in the hub. The sensor arrangement measures the angular acceleration of the driven wheel as the signal indicative of the force acting on the mobile wheeled device. The controller (64) is arranged at the driven wheel and controls the drive current to the electric motor in dependence on the measured angular acceleration.

Description

Technical Field

[0001] This invention relates to a mobile wheeled device comprising a plurality of non-drive wheels and a wheel driven by an electric motor. Background Technology

[0002] Mobile wheeled devices, such as hospital beds, mobile patient lifts, shopping carts, wheeled tables, trolleys, transport containers, or waste containers, are typically equipped with wheels to allow them to move easily. These wheels can be fixed wheels, swivel casters, or a combination thereof. The use of swivel casters makes it easier for personnel to guide the mobile wheeled device in the desired direction.

[0003] Because such wheeled mobile devices typically carry a considerable weight, they can be quite heavy for people. Therefore, similar to electric bicycles, motors can be used to assist people in propelling the wheeled mobile devices.

[0004] US 2015 / 0216487 discloses an example of such a device, illustrating a medical device in the form of a hospital bed with a base having four wheels. These wheels, or some of them, may be driven by a motor arranged on the base. Force sensors are arranged, for example, on a handle or guide device that enables an operator to move the medical device, such that the force sensors detect the force applied by the operator pushing or pulling the medical device. A controller can then activate the motor based on the force detected by the force sensors, thereby assisting the operator in moving the medical device.

[0005] However, in such medical devices, multiple different components, such as force sensors, controllers, and motors, are located in different parts of the device. This necessitates electrical connections between the force sensors and controllers, as well as between the controllers and motors. Furthermore, a mechanical connection is required between the motors and the wheels. Summary of the Invention

[0006] Therefore, the purpose of embodiments of the present invention is to provide a simpler solution that eliminates the need for electrical and mechanical connections between multiple components, while still enabling the operator to move the mobile wheeled device by efficiently driving one or more wheels of the mobile wheeled device according to the force exerted by the operator pushing or pulling the mobile wheeled device.

[0007] According to an embodiment of the invention, this objective is achieved in a mobile wheeled device comprising: a base including a plurality of non-drive wheels and a wheel driven by a motor; a sensor device arranged to detect a signal indicating a force acting on the mobile wheeled device from the outside; and a controller configured to drive the motor of the drive wheel based on the signal detected by the sensor device. The motor is contained in the hub of the drive wheel; the sensor device is arranged in or at the drive wheel and includes a rotary encoder arranged in the hub, wherein the sensor device is configured to measure the angular acceleration of the drive wheel as a signal indicating a force acting on the mobile wheeled device from the outside; and the controller is arranged in or at the drive wheel and configured to control the drive current supplied to the motor based on the measured angular acceleration.

[0008] By arranging the motor, along with sensor devices and controllers, in or at the drive wheels, the drive wheels can operate autonomously, independent of the circuitry arranged on the mobile wheeled device itself. Since the angular acceleration, which can be easily measured in the wheels, is proportional to the linear acceleration of the mobile wheeled device, the angular acceleration for a given weight of the mobile wheeled device is also proportional to the force acting on it externally, such as the force from a person pushing or pulling it. Furthermore, the auxiliary torque delivered to the mobile wheeled device by the motor in the drive wheels is proportional to the drive current supplied to the motor. Therefore, although the mobile wheeled device is driven by autonomous wheels, it is driven by an auxiliary torque directly related to the force applied to it by a person pushing or pulling it, thus reflecting the person's intention.

[0009] In one embodiment, the base may be arranged to define a generally rectangular shape and include four wheels, each of which is located at one corner of the generally rectangular shape. In this case, the four wheels located at the respective corners of the generally rectangular shape may be three non-drive wheels and one drive wheel.

[0010] In another embodiment, the base may be arranged to define a generally triangular shape and include three wheels, each of which is located at one corner of the generally triangular shape. In this case, the three wheels located at the respective corners of the generally triangular shape may be two non-drive wheels and one drive wheel.

[0011] In one embodiment, at least one point of the mobile wheeled device defines a plane arranged parallel to the surface on which the mobile wheeled device is placed. Drive wheels may be arranged in swivel casters connected to the base via axles arranged perpendicular to the plane and allowing the swivel casters to rotate about the longitudinal axis of the axles. Arranging drive wheels in swivel casters makes it easier for personnel to guide the mobile wheeled device in the desired direction. An electrical connection can be established between the base and the swivel casters via slip rings.

[0012] In one embodiment, the controller is configured to control the drive current supplied to the motor in such a way that it increases the drive current to the motor when the measured angular acceleration exceeds a positive threshold, decreases the drive current to the motor when the measured angular acceleration is below a negative threshold, and keeps the drive current to the motor constant when the measured angular acceleration is between the negative and positive thresholds. In this way, very smooth motor control is achieved, wherein irregular walking patterns of personnel pushing or pulling the wheeled mobile device do not affect the control.

[0013] In one embodiment, the swivel caster includes a swivel lock or a directional lock, which is configured in a locked position to prevent the swivel caster from rotating, and the controller is configured to drive the motor only when the swivel lock is in its locked position. In this way, it is ensured that current is supplied to the motor only when the swivel caster is locked in the proper position (e.g., when the wheel is aligned with the longitudinal axis of the movable wheel assembly).

[0014] In one embodiment, the swivel caster includes a brake configured in a braking position to prevent the drive wheel from rotating or rolling, and the controller is configured to drive the motor only when the brake is not in its braking position. In this way, it is ensured that current is supplied to the motor only when the wheel is freely rotating.

[0015] The sensor device can also be configured to measure the angular velocity of the drive wheels, and the controller can also be configured to drive the motor based on the measured velocity. As an example, the measured velocity can be used to detect the direction of movement of a mobile wheeled device. Therefore, a positive velocity can indicate that the swivel caster is moving in the forward direction, while a negative velocity can correspondingly indicate that the swivel caster is moving in the backward direction.

[0016] In one embodiment, the swivel caster also includes a tilt detector arranged to determine the component of gravitational acceleration in the longitudinal direction of the mobile wheeled device, and the controller is further configured to drive the motor of the drive wheel according to the determined component of gravitational acceleration. In this way, the drive wheel can automatically compensate for the additional force required for the mobile wheeled device to move uphill and the reduced force required to move downhill.

[0017] In this case, the controller can be configured to determine the tilt compensation current based on the determined gravitational acceleration component, and to drive the motor of the drive wheel by combining the drive current determined based on the measured angular acceleration with the tilt compensation current.

[0018] In one embodiment, the tilt detector includes a three-dimensional DC-response accelerometer arranged to measure gravitational acceleration relative to a defined plane. Alternatively, the tilt detector may include an angle measuring device arranged to determine an angle between the defined plane and a horizontal plane parallel to the surface on which the mobile wheeled device is placed, and a controller further configured to determine a component of gravitational acceleration from the determined angle.

[0019] Mobile wheeled devices can be used as hospital beds. Attached Figure Description

[0020] Embodiments of the invention will now be described more fully with reference to the accompanying drawings, in which: Figure 1 A hospital bed is shown as an example of a mobile device in which the present invention can be implemented. Figure 2 It shows the use in Figure 1 An example of swivel casters with drive wheels in a hospital bed. Figure 3 A cross-sectional view of the top component of a swivel caster with a slip ring is shown. Figure 4 It shows in Figure 2 A schematic diagram of a wheel with a motor integrated into the hub of a swivel caster. Figure 5 A rotary encoder is shown, featuring an optical sensor and optical pattern arranged on a circular ring element. Figure 6 It shows the use of Figure 4 An example of a motor control system, Figure 7 This illustrates the method for controlling the feed based on the measured angular acceleration. Figure 4 An example of a control strategy for the drive current of a motor. Figure 8 It shows additional functions Figure 6 The control system Figure 9 It shows a device including a tilt detector. Figure 8 The control system Figure 10 This illustrates measuring gravitational acceleration in a bed placed on a horizontal surface. Figure 11 The measurement of gravitational acceleration in a bed placed on an inclined surface is shown, and Figure 12 Another different hospital bed is shown as an example of a mobile device in which the present invention can be implemented. Detailed Implementation

[0021] As an example of a mobile wheeled device to which the present invention can be applied. Figure 1 A hospital bed 1 is shown. It should be noted that the invention can also be applied to other types of mobile wheeled devices, such as mobile patient lifts, shopping carts, wheeled tables, trolleys, transport containers, or waste containers.

[0022] The hospital bed 1 has a base 2 that defines a generally rectangular shape, and swivel casters are arranged at each corner of the base 2, namely three swivel casters 3, 4 and 5 with non-drive wheels 7, 8 and 9, and one swivel caster 6 with drive wheel 10. The drive wheel 10 is used to assist in the movement of the hospital bed 1, thereby making it easier for personnel to push or pull the bed.

[0023] It should be noted that the approximate rectangular shape defined by the base 2 need not be precisely rectangular. Therefore, if, for example, the two front wheels are arranged such that the distance between them is shorter than the distance between the two rear wheels, the base can be slightly trapezoidal in shape. Furthermore, it should be noted that although the base 2 defines the approximate rectangular shape by the four corners where the swivel casters are arranged, the base itself can have other forms.

[0024] It should also be noted that, although described here and in Figure 1 The embodiment shown is equipped with four swivel casters: three swivel casters with non-drive wheels and one swivel caster with a drive wheel. However, in other embodiments, some or all of the wheels may be arranged as fixed wheels. Furthermore, more than one wheel may be a drive wheel.

[0025] Two lifting columns 11 and 12, arranged on the base 2, support the bed frame 13, which can be raised or lowered via the lifting columns 11 and 12. Multiple bed sections 14, 15, and 16 can be tilted on the bed frame 13 via one or more linear actuators 17. A power supply 21 is also arranged on the bed frame 13 to supply power to, for example, the lifting columns 11 and 12 and the one or more linear actuators 17. The power supply 21 can be a power source connected to mains power, a battery-powered power source, or a combination thereof.

[0026] The swivel caster 6, which has drive wheels 10, is also connected to a power source 21 via cable 22, so that the motor (described below) that drives the wheels 10 can be powered. As an alternative to powering the motor in the wheels 10 from the power source 21 via cable 22, a rechargeable or replaceable battery can be arranged in the swivel caster 6.

[0027] A handle or foot pedal 23 is arranged on the base 2, near the swivel caster 6 with drive wheel 10 (as shown here) or on the swivel caster 6 itself. In one position of this handle, for example when pushed upward, the caster can be locked in a given position (i.e., to prevent rotation), and in another position of this handle, for example when pushed downward, the wheel 10 can be braked or locked (i.e., to prevent rotation within the swivel caster 6). Alternatively, separate handles / foot pedals can be used to perform these functions.

[0028] Furthermore, the four corners of the rectangular base 2 define a plane 24 arranged parallel to the surface on which the hospital bed 1 is placed. Therefore, when the hospital bed 1 is placed on a horizontal surface, plane 24 is also a horizontal plane. In other embodiments, the plane arranged parallel to the surface on which the mobile wheeled device is placed may be defined by one or more other corners or points of the mobile wheeled device.

[0029] Figure 2 A swivel caster 6 with drive wheels 10 is shown in more detail. The swivel caster 6 has a top component 25 that is fixed relative to the base 2 by a mounting rod or mounting shaft 26 having a central axis 27 and being arranged to be received in a mating hole in the base 2 such that the central axis 27 is perpendicular to the plane 24.

[0030] The drive wheel 10 is mounted on a fork 31, which is connected to a fixed top component 25 via a swivel joint (not shown). The swivel joint allows the fork 31, and thus the wheel 10, to rotate freely 360 degrees about the central axis 27 of the mounting shaft 26. A hub 33 is arranged around the central axis 32 of the wheel 10. It should be noted that there is a certain offset distance between the central axis 27 of the mounting shaft 26 and the central axis 32 of the wheel 10, which allows the swivel casters 6 to follow the direction of movement of the hospital bed. Figure 2 The wheel 10 is also shown to have a tread 34 and a wheel cover 35, with a motor that drives the wheel located behind the wheel cover.

[0031] As mentioned above, the swivel caster 6 is powered via cable 22 connected to the top component 25. In the top component 25, a slip ring device (described below) ensures that power can be delivered to the rotating parts of the caster 6, namely the motor that drives the wheel, and other circuitry, via cable 36 attached to the fork 31.

[0032] Figure 3A cross-sectional view of the top component 25 is shown, illustrating an embodiment of a slip ring 41 comprising two annular printed circuit boards. The lower printed circuit board 42 is attached to the rotating portion of the caster 6, i.e., the fork 31, and is provided with a plurality of circular circuit traces 43. The upper printed circuit board 44 is attached to the fixed top component 25 and is provided with a plurality of sliding contacts 45 arranged to contact the circuit traces 43 on the lower printed circuit board 42. Although not shown, the sliding contacts 45 are connected to cable 22, and the circuit traces 43 are connected to cable 36. Alternatively, the circuit traces may be arranged on the upper printed circuit board 44 and the sliding contacts on the lower printed circuit board 42, or other types of contacts may be used.

[0033] like Figure 2 As shown, hole 37 is arranged in mounting shaft 26. This hole 37 can receive the shaft of foot pedal 23, and the caster can be locked in a given position (i.e., prevented from rotating) by a well-known (but not shown) mechanism in swivel caster 6, and wheel 10 can be braked or locked (i.e., prevented from rotating in swivel caster 6).

[0034] Figure 4 A schematic structure of an example wheel 10 is shown, with the motor 51 contained in the hub 33. Figure 4 The motor 51 shown is a brushless DC motor with a so-called external rotor or outer rotor configuration, wherein electromagnets 52 (each electromagnet having a stator winding or stator coil wound around an iron core) form the center (iron core) of the motor, while permanent magnets 53 are arranged within an outer suspended rotor or annular component 54 surrounding the iron core. The tread 34 of the wheel 10 is arranged outside the annular component 54. It should be noted that... Figure 4 The number of electromagnets 52 and permanent magnets 53 shown is merely an example. Many other combinations can be used.

[0035] The electronic control circuit 61, which will be described in detail below, continuously switches the current in the motor phases to the stator windings to keep the motor rotating, based on signals from, for example, a Hall effect sensor (which provides information about the orientation and position of the rotor relative to the stator coils). This ensures proper commutation of the brushless DC motor 51. Along with other electronic components, this control circuit can be arranged on a printed circuit board 55 fixed to the stator portion of the motor and thus also included in the hub 33.

[0036] To ensure that the motor 51 can be driven based on the force acting on the hospital bed 1 from the outside, and thus the wheel 10, a rotary encoder is arranged in the wheel 10. The rotary encoder includes an optical sensor 56 arranged on a printed circuit board 55 and an optical pattern 59 arranged on a circular ring element 58 attached to a wheel cover 57, which is similar to the wheel cover 35 on the other side of the wheel 10. This is in Figure 5As shown in the diagram. Therefore, the optical sensor 56 is fixed to the stator portion of the motor, while the optical pattern 59 rotates together with the rotor portion of the motor, thereby allowing the sensor 56 to detect the position of the wheel by passing through the optical pattern 59 during the rotation of the wheel 10.

[0037] Figure 6 An example of a control system for the brushless DC motor 51 used in wheel 10 is shown. In this example, basic control of the motor 51 (i.e., synchronization of the current in the stator windings with the actual position of the rotor magnets) is performed by a BLDC controller 61 and a drive circuit 62 based on signals from a Hall effect sensor 63 (which provides information about the position of the rotor magnets relative to the stator coils). This type of control is well-known and will not be described in further detail here. The BLDC controller 61 and drive circuit 62 are mounted on a printed circuit board 55, as shown... Figure 5 As shown.

[0038] It should be noted that since the optical sensor 56 detects the position of the wheel and therefore also the position of the rotor magnet 53 relative to the stator coil 52, the signal from this sensor can also be used by the BLDC controller 61 to synchronize the current in the stator windings with the actual position of the rotor magnet when the motor is running. However, this sensor only provides relative position information of the magnet, so the signal from the Hall effect sensor 63 is still needed during motor startup, and occasional synchronization with the Hall element during motor operation may also be advantageous.

[0039] According to the present invention, the auxiliary propulsion provided by the wheel 10 to the hospital bed is provided by controlling the drive current supplied to the motor 51 based on the measured angular acceleration of the wheel 10. Therefore, Figure 6 It is also shown that a main controller 64, configured to control the drive current to the motor 51 based on the measured angular acceleration of the wheel 10, can be arranged on a printed circuit board 55. Figure 5 The diagram illustrates one possible arrangement of the main controller 64 on the printed circuit board 55. It should be noted that in some embodiments, the functionality of the BLDC controller 61 may be integrated into the main controller 64.

[0040] Angular acceleration is continuously determined by a sensor device 65 including a rotary encoder (i.e., optical pattern 59 and optical sensor 56) and an acceleration calculation unit 66. In this embodiment, the acceleration calculation unit 66 is integrated into the main controller 64, but acceleration calculation can also be performed in a separate circuit.

[0041] As the optical pattern 59 rotates with the wheel 10, the optical sensor 56 generates a series of pulses, each pulse indicating the wheel's position. Based on these pulses, the acceleration calculation unit 66 can continuously determine the wheel's current angular velocity and current angular acceleration. The velocity can be determined, for example, by counting the number of pulses within a predetermined time window, measuring the time between two successive pulses, or by other known algorithms for this purpose. Since acceleration is defined as the change in measured velocity, acceleration can then be determined from the velocity. Alternatively, several known algorithms exist for determining angular acceleration directly from the pulses of the optical sensor 56. Examples of such algorithms are those using correlation matrices or correlation tables.

[0042] Since the angular acceleration of wheel 10 is proportional to the linear acceleration of the hospital bed, for a given bed weight, the angular acceleration of the wheel is also proportional to the force acting on the bed from the outside (e.g., the force from a person pushing or pulling the bed). Therefore, at any given time, the angular acceleration measured locally in the wheel is a direct signal indicating the force acting on the hospital bed from the outside, and thus also a signal indicating the intention of the person pushing or pulling the bed.

[0043] As described above, the auxiliary propulsion provided to the hospital bed 1 by the drive wheels 10 is controlled by adjusting the drive current supplied to the motor 51 based on the measured angular acceleration of the wheels. Controlling the drive current is advantageous because the auxiliary torque delivered to the hospital bed 1 by the motor 51 in the drive wheels is proportional to the drive current supplied to the motor. Therefore, although the hospital bed 1 is driven by its own wheels, it is driven by an auxiliary torque directly related to the force applied to the bed by the person pushing or pulling it, thus reflecting the person's intention.

[0044] Based on the measured angular acceleration, the current calculation unit 67 can continuously determine the auxiliary current I according to the desired control strategy described below. ass Then, the auxiliary current I can be... ass The required current I used for driving motor 51 req One control strategy is to simply make the auxiliary current I... ass It is proportional to the measured angular acceleration of the wheel. This provides quick and direct control of the motor, but the control may also tend to be somewhat "nervous" as it tries to follow the irregular walking patterns of the person pushing or pulling the bed.

[0045] Another control strategy to overcome this drawback is... Figure 7 As shown in the diagram. This strategy uses two thresholds, namely a positive threshold α for the measured angular acceleration of the wheel. th+ and negative threshold a th- For the smallest measured value of angular acceleration, i.e., at a... th- and a th+ Between, auxiliary current Iass Remain unchanged, such as Figure 7 In t o The values ​​between t1, t2 and t3, and t4 and t5 are shown. However, when the measured angular acceleration exceeds the positive threshold α... th+ For example, Figure 7 As shown between t1 and t2, regardless of whether the acceleration exceeds the threshold a th+ How much, auxiliary current I ass They all increase linearly, for example, at a rate of 5 mA / 10 ms. Similarly, when the measured angular acceleration is below the negative threshold a... th- For example, Figure 7 As shown between t3 and t4, regardless of whether the acceleration is below the threshold a th- How much, auxiliary current I ass The current decreases linearly, for example, at a rate of -10mA / 10ms. In this way, very smooth motor control is achieved, where irregular walking patterns of personnel pushing or pulling the bed do not affect the control.

[0046] The control strategy may also include a braking function. If the user (i.e., the person pushing or pulling the bed) initiates a large deceleration, the auxiliary current I... ass It will decrease rapidly and eventually provide braking force. Therefore, as an example, if the measured angular acceleration is significantly below the aforementioned negative threshold α... th- If the (negative) braking threshold is reached, the auxiliary current I will first be reduced by a relatively low value. ass For example, at the rate of -10mA / 10ms mentioned above, and then it can be reduced, for example, by doubling every 100ms until the maximum reduction is reached. If the auxiliary current I during this process ass Dropping below zero means that braking force will be provided.

[0047] Since the BLDC controller 61 (and thus the motor 51) is controlled by voltage rather than current, a feedback loop for driving the current is arranged. The current detector 68 measures the actual current I drawn by the motor. meas And in the motor regulator 69, the actual current I meas With the determined required current l req The comparison is performed, and the output voltage supplied to the BLDC controller 61 is continuously adjusted so that the actual current I... meas Maintain compliance with required current I req .

[0048] Although, as described above, the current calculation unit 67 determines the auxiliary current I based on the measured angular acceleration. ass However, other signals may also affect the determined required current l. req Therefore, as mentioned above... Figure 1 and Figure 2 The caster 6 can be locked in a given position (i.e., to prevent rotation), and the wheel 10 can be braked or locked (i.e., to prevent rotation within the caster 6). These locking mechanisms may include detectors indicating their locking status. Therefore, Figure 8 A wheel lock detector 71 is shown that provides a signal to the current calculation unit 67 indicating whether the wheel 10 is locked. The current calculation unit 67 can then be configured to provide the output signal 1 only when the wheel is unlocked. req Similarly, Figure 8 A swivel lock detector 72 is shown that provides a signal to the current calculation unit 67 indicating whether the swivel caster 6 is locked. The current calculation unit 67 can then be configured to provide an output signal 1 only when the swivel caster is locked in the appropriate position. req For example, the position where wheel 10 is aligned with the longitudinal axis of hospital bed 1. Note that wheel 10 can be aligned with the longitudinal axis of hospital bed 1 in two opposite directions, so the omnidirectional lock detector 72 can also be configured to provide a signal to the current calculation unit 67 indicating the direction in which the omnidirectional caster 6 is locked.

[0049] As mentioned, the acceleration calculation unit 66 can determine the current angular acceleration and current angular velocity of the wheel 10 based on the pulses received from the optical sensor 56. Therefore, as Figure 8 As shown, the signal of the angular velocity of the indicator wheel 10 can also be provided to the current calculation unit 67. Here, for example, it can be used to detect the direction of movement of the hospital bed 1. Therefore, a positive velocity can indicate that the swivel caster 6 is moving in the forward direction, while a corresponding negative velocity can indicate that the swivel caster 6 is moving in the backward direction. The measured velocity can also affect the determination of the auxiliary current I based on the measured angular acceleration. ass This is the method. For example, when the measured angular acceleration exceeds a positive threshold α... th+ Time auxiliary current I ass like Figure 7 The linearly increasing rate shown can depend on the measured speed; for example, a higher rate can be used for low speeds.

[0050] Hospital beds are not always placed or moved on a perfectly level surface. Instead, they sometimes must be moved up or down a slope, which can affect the bed's movement. To take this into account, the swivel casters 6 may also include tilt detectors 75, such as... Figure 9 As shown and as Figure 5 The tilt detector shown can be arranged on a printed circuit board 55. In one embodiment, the tilt detector 75 includes a three-dimensional accelerometer arranged to measure gravitational acceleration relative to a plane 24 defined by the respective corners of the rectangular base 2. The accelerometer is a DC-response accelerometer, which can be used to measure static acceleration, such as gravity.

[0051] Figure 10 The image shows bed 1 when placed on a horizontal surface. Therefore, plane 24 is also a horizontal plane. Tilt detector 75 is configured to measure gravitational acceleration along three orthogonal axes (i.e., the X-axis, Y-axis, and Z-axis). The X-axis and Y-axis lie in a plane parallel to plane 24, i.e., in… Figure 10 The plane is horizontal, with the X-axis along the longitudinal direction of hospital bed 1, and the Z-axis perpendicular to plane 24. Therefore, in Figure 10 In this scenario, when the bed is placed or moved on a horizontal surface, the tilt detector 75 will not measure gravitational acceleration on the X or Y axis, but will measure acceleration g (i.e., gravitational acceleration) along the Z axis. Since no gravitational acceleration is measured in the longitudinal direction (i.e., along the X-axis) of the hospital bed 1, the movement of the bed is unaffected, and the auxiliary current I determined in the current calculation unit 67 based on the measured angular acceleration, as described above, is... ass Used as the determined required current I req .

[0052] exist Figure 11 The image shows bed 1 when placed on an incline with an angle α relative to a horizontal surface. Therefore, angle α also defines the angle between plane 24 and the horizontal plane. In the tilt detector 75, gravitational acceleration is now measured as the longitudinal acceleration component a along the X-axis. x and the vertical acceleration component a along the Z-axis z The longitudinal component a of gravitational acceleration x The size is equal to a x = g tan(α), and due to its longitudinal direction, it affects the hospital bed with a force in the same or opposite direction as the force acting on the bed from the outside (e.g., from a person pushing or pulling the bed). Therefore, if the bed is pushed uphill, an additional force is required due to the longitudinal component of gravitational acceleration, while correspondingly less force is required when the bed is pushed downhill.

[0053] To compensate for this effect, the current calculation unit 67 is configured to determine the longitudinal acceleration component a measured by the tilt detector 75. x Proportional gravity-compensated current I grav It should be noted that when the bed is pushed uphill (i.e., when the longitudinal acceleration component a...), x When the direction of the force pushing the bed is opposite to the direction of the force, the gravity compensation current I... grav It will have a positive value. Correspondingly, when the longitudinal acceleration component a... x When the force pushing the bed has the same direction as the force pushing the bed (i.e., when the bed is pushed downhill), this value will be negative. In the current calculation unit 67, the gravity compensation current I is then... grav The auxiliary current I, determined as described above based on the measured angular acceleration, is... assSum and use as the determined required current I req Therefore, I req =I ass +I grav In this way, the drive wheel 10 can automatically compensate for the extra force required by the bed when it moves uphill and the reduced force required when it moves downhill.

[0054] Furthermore, in some cases, this solution can prevent the hospital bed 1 from rolling on its own if it remains on the ramp without being braked, because in this case the angular acceleration measured by sensor device 65 consists only of the longitudinal acceleration component a. x This is caused by, therefore, through the appropriate selection of coefficients, I ass and I grav They can cancel each other out.

[0055] In the above embodiment, the tilt detector 75 uses a three-dimensional accelerometer configured to measure gravitational acceleration along three orthogonal axes (i.e., the X-axis, Y-axis, and Z-axis), thereby determining the longitudinal acceleration component a along the X-axis. x The longitudinal acceleration component is used to determine the gravity compensation current I due to its longitudinal orientation. grav Alternatively, different types of tilt detectors can be used. As an example, an angle measuring device or inclinometer can be used to measure the angle α, and then the longitudinal acceleration component a can be measured. x Determined as a x = g tan(α).

[0056] In the above embodiments, a mobile wheeled device in the form of a hospital bed 1 is described, which has a base 2, the base defining a generally rectangular shape, and swivel casters provided at each corner of the base 2, namely three swivel casters 3, 4, and 5 with non-drive wheels 7, 8, and 9, and one swivel caster 6 with drive wheel 10. However, it should be noted that the shape of the base and the number of wheels may differ from these embodiments. As an example, Figure 12 A bed 101 is shown, having a base 102 that defines a generally triangular shape. At each corner of the base 102 are casters: two casters 3 and 5 with non-drive wheels 7 and 9, and one caster 6 with a drive wheel 10. Also here, some or all of the wheels may be arranged as fixed wheels. Furthermore, more than one wheel may be a drive wheel.

[0057] Although various embodiments of the invention have been described and illustrated, the invention is not limited thereto, but may be practiced in other ways that fall within the scope of the subject matter defined by the appended claims.

Claims

1. A mobile wheeled device (1), comprising: The base (2) includes multiple non-drive wheels (7, 8, 9) and a wheel (10) driven by a motor (51); A sensor device (65) is arranged to detect a signal indicating a force acting from the outside on the movable wheeled device (1); as well as The controller (64) is configured to drive the motor (51) of the drive wheel (10) based on signals detected by the sensor device (65). Its features are: The motor (51) is contained in the hub (33) of the drive wheel (10); A sensor device (65) is disposed in or at the drive wheel (10) and includes a rotary encoder (56, 59) disposed in the hub (33), wherein the sensor device is configured to measure the angular acceleration of the drive wheel (10) as a signal indicating the force acting from the outside on the movable wheeled device (1); and The controller (64) is located in or at the drive wheel (10) and configured to control the drive current (I) supplied to the motor (51) based on the measured angular acceleration. ass ).

2. The mobile wheeled device according to claim 1, characterized in that, The base (2) is arranged to define a generally rectangular shape and includes four wheels (7, 8, 9, 10), each of which is arranged at one corner of the generally rectangular shape.

3. The mobile wheeled device according to claim 2, characterized in that, The four wheels arranged at the corners of the generally rectangular shape are three non-drive wheels (7, 8, 9) and one drive wheel (10).

4. The mobile wheeled device according to claim 1, characterized in that, The base (102) is arranged to define a generally triangular shape and includes three wheels (7, 9, 10), each of which is arranged at one corner of the generally triangular shape.

5. The mobile wheeled device according to claim 4, characterized in that, The three wheels arranged at the corners of the generally triangular shape are two non-driving wheels (7, 9) and one driving wheel (10).

6. The mobile wheeled device according to any one of claims 1 to 5, characterized in that, At least one point of the movable wheel device (1) defines a plane (24) arranged parallel to the surface on which the movable wheel device (1) is placed, and a drive wheel (10) is arranged in a swivel caster (6) which is connected to the base (2) via an axle (26) arranged perpendicular to the plane (24) and allows the swivel caster (6) to rotate about the longitudinal axis (27) of the axle (26).

7. The mobile wheeled device according to claim 6, characterized in that, An electrical connection is established between the base (2) and the swivel caster (6) via a slip ring (41).

8. The mobile wheeled device according to any one of claims 1 to 7, characterized in that, The controller (64) is configured to control the drive current supplied to the motor (51) in the following manner: When the measured angular acceleration exceeds the positive threshold (a th+ Increase the drive current supplied to the motor (51) when ) When the measured angular acceleration is below the negative threshold (a th- When ), reduce the drive current supplied to the motor (51), and When the measured angular acceleration is within the negative threshold (a th- ) and positive threshold (a th+ The drive current supplied to the motor (51) remains constant between ) and ).

9. The mobile wheeled device according to claim 6 or 7, characterized in that, The swivel caster (6) includes a rotary lock, which is configured to prevent the swivel caster (6) from rotating in the locked position, and wherein the controller (64) is configured to drive the motor (51) only when the rotary lock is in its locked position.

10. The mobile wheeled device according to claim 6 or 7, characterized in that, The omnidirectional caster (6) includes a brake, which is configured in the braking position to prevent the drive wheel (10) from rotating, and wherein the controller (64) is configured to drive the motor (51) only when the brake is not in its braking position.

11. The mobile wheeled device according to any one of claims 1 to 10, characterized in that, The sensor device (65) is also configured to measure the angular velocity of the drive wheel (10), and the controller (64) is also configured to drive the motor (51) according to the measured angular velocity.

12. The mobile wheeled device according to claim 6 or 7, characterized in that, The omnidirectional caster (6) also includes a tilt detector (75), which is arranged to determine the longitudinal component of gravitational acceleration (α) of the movable wheeled device (1). x ),and The controller (64) is also configured to adjust according to the determined gravitational acceleration component (a x The motor (51) of the drive wheel (10) is used to drive the drive wheel (10).

13. The mobile wheeled device according to claim 12, characterized in that, The controller (64) is configured to adjust according to the determined gravitational acceleration component (a x ) to determine the tilt compensation current (I grav ), and use the driving current (I) determined based on the measured angular acceleration. ass ) and tilt compensation current (I grav The motor (51) of the drive wheel (10) is driven by a combination of these components.

14. The mobile wheeled device according to claim 12 or 13, characterized in that, The tilt detector (75) includes a three-dimensional DC response accelerometer arranged relative to a defined plane (24) to measure gravitational acceleration.

15. The mobile wheeled device according to claim 12 or 13, characterized in that, The tilt detector (75) includes an angle measuring device arranged to determine an angle (α) between a defined plane (24) and a horizontal plane, the defined plane being parallel to the surface on which the movable wheeled device is placed, and a controller (64) is further configured to determine a component of gravitational acceleration (α) from the determined angle (α). x ).

16. The mobile wheeled device according to any one of claims 1 to 15, characterized in that, The mobile wheeled device (1) is a hospital bed.

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