DK181088B1

DK181088B1 - Actuator system, piece of furniture with an actuator system and method for controlling an actuator system

Info

Publication number: DK181088B1
Application number: DKPA202170212A
Authority: DK
Inventors: Lukas Stefan
Original assignee: Logicdata Electronic & Software Entw Gmbh
Priority date: 2020-05-15
Filing date: 2021-05-06
Publication date: 2022-12-09
Also published as: DE102020113256A1; CN215897491U; DK202170212A1

Abstract

Actuator system, piece of furniture with an actuator system and method for controlling an actuator system. An actuator system, in particular for adjusting a piece of furniture, comprises a motor (102) with a system of rotating shafts which are driven by the motor in dependence on one another, a conversion arrangement (200) which comprises one of the rotating shafts and is arranged to convert a rotational movement of this shaft generated by the motor into an elongation of the actuator system. The actuator system further comprises a braking device (103) having at least one rechargeable energy storage device (500) arranged to supply energy to a controller (101) and the braking device (103) during a braking phase. The braking device (103) is adapted to reduce a speed of rotational movement of one of the rotating shafts. The actuator system further comprises a locking device (104) coupled to one of the rotating shafts and adapted to selectively cause rotational locking of that shaft, and a controller (101) for controlling the motor, the braking device (103), and the locking device (104).

Description

DK 181088 B1 1 Description Actuator system, piece of furniture with an actuator system and method for controlling an actuator system The present disclosure relates to an actuator system, a piece of furniture comprising such an actuator system, and a method for controlling such an actuator system.

Adjustable furniture is known both in the field of office furniture and in the home sector. The most common designs in the office furniture sector are, for example, electrically adjustable tables or chairs, while electrically adjustable beds, seating furniture or reclining furniture are known in the home sector.

The adjustment is usually performed by linear actuators or similar actuator systems built into one or more columns of the table or in a frame of the bed, seating furniture or reclining furniture.

Such actuators are regularly formed by an electric motor, which drives a motor shaft, and a conversion device, which converts a rotation of a shaft into a linear displacement of the actuator. For example, spindle-nut systems are used as such conversion arrangements, where a spindle is driven by the motor shaft via a gearbox and causes a linear displacement of the nut. Using the example of a table, this then leads to the raising or lowering of the table top.

However, to ensure that a force acting in a linear direction on the actuator, for example through a tabletop, does not lead to a reverse rotation of the spindle or motor shaft, the

DK 181088 B1 2 components acting together are generally designed accordingly. For example, a friction between the components is deliberately chosen to be high enough to create self- locking. However, the degree of self-locking also determines the efficiency of the actuator. Accordingly, more energy must be expended for linear adjustment of the actuator with a high degree of self-locking than with low or non-existent self- locking. In the case of conventional linear actuators and similar actuator systems, a balance must therefore be struck between acceptable efficiency and the need for self-locking. In self-locking linear actuators, the degree of self-locking is typically selected so that the linear actuator holds the load, e.g. of the table top, with or without loading, in the event of a supply voltage failure. If a supply voltage failure occurs while the load is moving, the self-locking brakes the load to a stop. However, the self-locking required for this results in significantly reduced efficiency. Alternatively, actuators are built with little or no self- locking, but then they must have an additional braking and/or holding arrangement. However, it turns out that a holding arrangement cannot realize a reliable locking function in the event of a power failure during e.g. a downward movement of a heavy or heavily loaded table top or wears out quickly.

One object to be solved is to provide an improved concept of an actuator system that overcomes the limitations of conventional solution.

This object is solved by the subject-matter of the independent claims. Designs and further developments are described in the dependent claims.

DK 181088 B1 3

The improved actuator concept 1s based on the idea of providing a non-self-locking actuator system for electrically adjustable furniture, in particular for electrically adjustable tables or beds, with high efficiency, which has a braking mechanism and a locking mechanism.

On the one hand, these mechanisms ensure a safe adjustment of an adjustable component of the piece of furniture, and on the other hand, they realize a safe holding of the adjustable component when no adjustment is performed.

The improved actuator concept is also based on the idea of at least partially supplying the braking mechanism with energy from a rechargeable energy storage device, in particular in the event of a failure of a supply voltage, in order to slow down an adjustment of the adjustable component in such a way that an adjustment speed is achieved which is not critical for the wear-free and reliable operation of the locking mechanism.

An actuator system according to the improved concept comprises a motor with a system of rotating shafts which are driven by the motor in dependence on each other, and a conversion arrangement which comprises one of the rotating shafts and is arranged to convert a rotational movement of this shaft generated by the motor into an elongation of the actuator system.

Further, the actuator system comprises a braking device comprising at least one rechargeable energy storage device arranged to supply energy to a controller and the braking device during a braking phase, the braking device being arranged to reduce a speed of rotational movement of one of the rotating shafts.

The actuator system further comprises a locking device coupled to one of the rotating shafts and adapted to selectively effect rotational locking of that shaft, and a controller for controlling the motor, the braking device, and the locking device.

DK 181088 B1 4 Accordingly, the improved drive concept proposes to selectively brake or selectively cancel a braking effect on a movement of the drive side, such as a shaft, in order to selectively brake or ultimately block a rotation of the shaft and thus of coupled shafts. Such a braking effect can be provided either for both possible directions of rotation of the shafts or alternatively only in a selected direction of rotation, while a second direction of rotation is possible without hindrance. In a motor having a system of rotating shafts driven by the motor in dependence on each other, a braking device is provided for this purpose, which comprises one of the rotating shafts as a braking shaft.

The braking device can produce an electrical braking effect by controlling the motor accordingly in order to brake the rotational movement of the motor shaft in a controlled manner. Alternatively, the braking effect can also be effected by a mechanical brake.

Examples of electric brakes include eddy current brakes, electromotive brakes in which the drive motor is used as a generator during braking, resistive or short-circuit brakes in which current generated by the motor is converted into heat via electrical resistors, reverse current brakes in which the electric motor is braked by reversing the polarity of the energy supply, and direct current brakes in which the electric motor is braked using direct current.

DE 10 2020 100 439 of the applicant describes a possible example of a mechanical braking device comprising at least one brake chamber formed between the brake shaft and an associated brake wall having a wall surface substantially

DK 181088 B1 parallel to an axis of rotation of the brake shaft, and for each brake chamber a brake body arranged in the brake chamber.

In order to achieve the selective braking effect, the brake chamber has at least two regions, namely one in

5 which the brake body is mounted in such a way that it has no contact with the brake shaft and thus generates no braking effect, and another region in which the radial distance between the brake wall and the axis of rotation decreases and in which the brake body can form a frictional contact with the brake wall and the brake shaft.

In the latter region, the braking effect thus increases as the distance between the brake shaft or axis of rotation and the brake wall decreases.

The rotating shaft system is formed, for example, by a motor shaft, which is rigidly connected to a rotor of the motor, a gear shaft of a speed reducer, which is coupled on the input side to the motor shaft and on the output side to a spindle of the conversion arrangement.

The spindle is thereby also a component of the rotating shaft system.

In alternative embodiments, for example in the case of a direct drive, the spindle may also be coupled directly to the motor shaft or alternatively be identical to the motor shaft.

In the latter case, the system of rotating shafts would consist of only one shaft, the motor shaft.

The brake shaft can basically be formed by any shaft of the system of rotating shafts.

Furthermore, the improved drive concept proposes to selectively lock a movement of the drive side, such as a motor shaft, thereby selectively causing a rotation lock of the motor shaft.

The rotation lock can be provided either for both possible directions of rotation of the motor shaft or, alternatively, only in a selected direction of rotation, while a second direction of rotation is unobstructed.

For

DK 181088 B1 6 this purpose, the actuator system is provided with a locking device coupled to a driven shaft, e.g. to the motor shaft, of the linear actuator and comprising a locking element arranged to selectively block or inhibit a rotational movement of the driven shaft in at least one direction. The shaft may be arranged in a common housing with the motor, or may be separate from the motor. The selective rotation lock makes it possible to design the linear actuator with a high degree of efficiency, for example through low friction. This can also result in reduced noise development of the linear actuator, for example through lower gear noise.

DE 10 2019 113 111 of the applicant describes a possible example of a locking device, which for this purpose comprises at least one locking element, an inner part with at least one inner chamber and an outer part radially surrounding the inner part with at least one outer chamber, wherein the inner chamber and the outer chamber can be aligned with respect to each other by rotation. The two chambers are configured such that the locking element can be clamped between the inner and outer chambers to activate the rotation lock.

The actuator system comprises, for example, a linear actuator arranged to translate the rotational movement of the motor shaft into an elongation of a component of the linear actuator. For example, a rotational movement of the motor shaft is translated into an adjustment of the height of a worktop of an adjustable table.

The control system can be a component of an actuator, i.e., it can be designed as a central control system, or it can be

DK 181088 B1 7 designed as a decentralized control system and be located outside the actuator.

A power supply, e.g. an external mains voltage, supplies the energy for the adjustable component of the furniture system, i.e. supplies at least the motor and the control as well as the braking and possibly the locking device of the actuator system.

The power supply has a mains connection for coupling to an external voltage source.

The rechargeable energy storage device of the braking device can be integrated into the voltage supply.

Alternatively, the rechargeable energy storage device is designed as a separate component with its own housing, which can be optionally connected to the power supply, for example, and can thus also be retrofitted.

If necessary, the energy storage device has its own power supply connection, e.g. implemented by a 5V USB power supply unit.

The aforementioned case of a mains voltage failure is particularly problematic for the operation of the braking and locking device.

In the absence of a supply of mains voltage, controlled braking is not possible.

To solve this problem, an actuator system according to the improved concept comprises said rechargeable energy storage device.

This is arranged to supply at least the control system and the braking device with a voltage so that controlled braking is possible even in the absence of mains voltage, so that the locking device, which comprises for example a mechanical locking mechanism, can effect the rotational locking of the shaft.

Optionally, the rechargeable storage device is further adapted to also supply the locking device with a voltage.

Energy is drawn from the energy storage device of the braking device for the duration of braking and, for example, only

DK 181088 B1 8 when no mains voltage is present. However, the duration of the energy extraction can also be further reduced if the rotational movement of the shaft is not reduced to a standstill by the braking device, but only up to a certain rotational speed which is non-critical for the holding arrangement. Non-critical in this context means that a speed of the rotational movement of the shaft is reached at which the locking device can reliably trigger the rotation lock.

In at least one embodiment, the controller is arranged to detect the failure of the mains voltage and to establish a supply of energy to the braking device from the energy storage device during the braking phase when the failure of the mains voltage is present.

If the controller detects that no mains voltage is available, but also that no load is being moved, i.e. no adjustment of an adjustable component of the furniture is in process, then no braking by the braking device is required and thus no energy from the energy storage device needs to be used for supply.

In at least one embodiment, the controller is further configured to detect whether a predefined braking effect of the rotational movement is caused by a gravitational force when the mains voltage fails. Furthermore, in such embodiments, the controller is set up to establish the supply of energy to the braking device from the energy storage during the braking phase if the gravitational force falls below the predefined braking effect. In this case, the predefined braking effect corresponds to a braking effect that is required to reduce the speed below a threshold value.

DK 181088 B1 9 For example, in the event of a power failure, the controller measures whether an adjustment of the adjustable component slows down without being braked by the braking device. This may be the case, for example, if the gravitational force acting on an adjustable tabletop or component of a bed slows down or completely brakes a height adjustment that is substantially parallel to the gravitational force or has at least one component that is parallel to the gravitational force of that tabletop. Specifically, in this case, the gravitational force slows the tabletop coming up when the voltage supply is disabled. Thus, the gravitational force slows the motion and no active braking is required. In this case, no energy from the energy storage device then needs to be used for supply, since the braking by the gravitational force is sufficient to achieve a speed of the rotational movement at which activation of the rotation lock is not critical.

In at least one embodiment, the controller is set up to operate the motor in a generator mode during a first partial phase of the braking phase, in which the energy storage device is charged with generated braking energy. Furthermore, during a second partial phase of the braking phase, the controller is set up to reduce the speed of the rotational movement to a value below a threshold value using the energy from the energy storage device.

Such designs implement the principle of regenerative braking, which is known from the automotive industry, for example, whereby kinetic energy is converted back into electrical energy by electric motors. In this case, the motor acts as a generator and uses the energy during the first partial phase, which can be referred to as the recuperation phase, to charge

DK 181088 B1 10 the energy storage device and optionally to supply the control system and the braking device, in particular in the event of a mains voltage failure.

In other words, the principle of the electric generator brake is used in the first partial phase, i.e. the kinetic energy or the position energy of the moving mass is converted into electrical energy.

By extracting the energy from the motion, the electric motor and thus the shafts driven by the electric motor are braked.

At the same time, the energy is used to charge the energy storage device.

At a certain speed of the shaft, however, the energy generated by the motor as a generator is no longer sufficient to charge the energy storage device or to supply the control system and the braking device with energy and thus maintain controlled braking.

Therefore, in this second partial phase, which can be referred to as the active braking phase, additional energy is used from the energy storage device, which was charged by the motor before the voltage failure from the mains voltage or during the recuperation phase.

In at least one embodiment, the controller is further configured to reduce the speed of the rotational movement using energy from the energy storage device in the event of a power supply failure.

In particular, if an external voltage supply fails, the braking process is completed during the second partial phase with energy from the energy storage device.

This ensures controlled braking of the rotational movement in order to achieve a rotational speed that is not critical for operation or activation of the locking device.

DK 181088 B1 11 In at least one embodiment, the controller is further adapted to use the energy from the energy storage device to change a motor terminal voltage during the second partial phase to reduce the speed of the rotational movement.

In at least one embodiment, the controller is further configured to reverse the motor terminal voltage. In at least one embodiment, the controller is further configured to continuously increase and decrease the motor terminal voltage.

The braking effect can be caused by changing the terminal voltage of the motor. The terminal voltage can be changed in its level, or the polarity can be reversed. Preferably, the voltage is changed continuously in order to brake the motor continuously. Reversing the polarity of the voltage corresponds to the principle of countercurrent braking.

In at least one embodiment, the controller is further adapted to use the energy from the energy storage device to establish a connection between a braking resistor and the motor during the second partial phase.

Alternatively or additionally, the supplied energy can be used to connect a resistor to the motor and thus convert the energy into heat. For example, a relay is switched to connect the resistor to the motor. In case of a mains voltage failure, the energy from the energy storage can be used to switch the relay. This corresponds to the principle of short- circuit or resistance braking. Short circuit in this context means a braking resistor with low electrical resistance.

DK 181088 B1 12 In at least one embodiment, the braking device comprises a mechanical brake and the controller is further arranged to use the energy from the energy storage device to establish a frictional connection of the mechanical brake with a shaft of the actuator system during the second partial phase.

Alternatively or additionally, the energy supplied from the battery can be used to actuate a mechanical brake.

In at least one embodiment, the controller is configured to detect whether the speed of the rotational movement is greater than a threshold value and to control the braking device such that the speed of the rotational movement is reduced to a value below the threshold value.

In at least one embodiment, the threshold value corresponds to a non-critical speed of the rotational movement for the locking device.

For example, the control system can detect the current speed of the rotational movement and activate braking by the braking device only if the detected speed is already low enough that the locking device can reliably lock the rotational movement even without additional braking by the braking device. The threshold value can correspond to the speed for which uncritical operation of the locking device is possible. The threshold value can be zero, for example.

In at least one embodiment, the energy storage device has a voltage less than or equal to 5 V.

In at least one embodiment, the energy storage device comprises one, in particular a single, secondary cell.

DK 181088 B1 13 A secondary cell is a single storage element that cannot be further divided. Secondary cells are components of accumulators in which the permanent storage of electrical energy is made possible with the aid of chemical reactions by applying an external voltage. Accumulators and secondary cells are forms of rechargeable energy storage in the power supply.

Since the energy from the rechargeable energy storage unit is only required for a relatively short period of time, in particular only during at least a partial phase of a braking process by the braking device, and only to supply the control unit and the braking device, an accumulator consisting of a large number of secondary cells is not necessary. Instead, a single secondary cell may suffice to perform a controlled braking operation in the event of a mains voltage failure. Typically, power on the order of 10-15 W is required for braking. In contrast, adjusting the height of a tabletop, for example, typically requires about 100-200 W of power. Consequently, designs with only a single secondary cell are distinguished from conventional systems that use an uninterruptible power supply to operate the adjustable furniture and therefore require much larger energy storage devices, such as large rechargeable batteries.

In at least one embodiment, the energy storage device comprises secondary cells connected in parallel.

Since an accumulator is a set of secondary cells connected in series and/or parallel, the charging circuitry is typically complex and additionally risky if the charging circuitry is poor. In such arrangements, care must be taken to ensure that

DK 181088 B1 14 all cells in the accumulator are charged reasonably evenly to prevent overcharging or deep discharge of individual cells. While secondary cells connected in parallel are still relatively easy to handle, secondary cells connected in series are more complex to charge. A single secondary cell or secondary cells connected in parallel can be well controlled in terms of temperature and state of charge. The charging circuit for such arrays can be implemented e.g. by a charging IC, or alternatively by a simple constant voltage method. In at least one embodiment, the energy storage device comprises a lithium cell.

Typical lithium cells have a nominal voltage of less than 5 V, in particular approx. 3.6-3.7 V, per cell. Thus, single or several lithium cells connected in parallel, which have the same nominal voltage with higher capacity, are well suited to be charged quickly, for example, by generator operation of the motor. Typically, about 5-15 W are generated in 100-200 ms of generator operation. Alternatively, the lithium cells can be charged by a power supply, for example a typical 5 V USB power supply, of the actuator system.

In at least one embodiment, the energy storage device comprises a supercapacitor. As an alternative to or in combination with secondary cells, the energy storage system can comprise supercapacitors. Also called ultracapacitors, these are electrochemical capacitors and as such are a further development of double-layer capacitors. Compared with accumulators of the same weight,

DK 181088 B1 15 supercapacitors have only about 10% of their energy density, but their power density is about 10-100 times greater. They can therefore be charged and discharged much faster and can also withstand significantly more switching cycles than secondary cells. Supercapacitors have a nominal voltage between approx. 2-4 V and are thus approximately in the same range as lithium cells. In addition, supercapacitors have a similar internal resistance in the mQ range. This low internal resistance allows large currents to be drawn. In at least one embodiment, the energy storage device has a power capacity less than 100 W, particularly in the range of 10-20 W. In at least one embodiment, the energy storage device has an energy capacity that is less than an energy required to operate the motor.

The energy storage device is only set up to ensure a controlled braking process by the braking device in the event of a mains voltage failure. For this purpose, the specified power capacity is sufficient to supply the control unit and the braking device with a voltage. In particular, the energy storage device is not set up to provide sufficient energy for adjusting the adjustable component of the furniture. In at least one embodiment, the braking device comprises a voltage converter. Due to the low voltage of a single secondary cell or supercapacitor, for example less than 5 V, and the usually

DK 181088 B1 16 required higher voltage for an electrically adjustable furniture system, for example about 20 V or more, a voltage converter stage is used to raise the voltage of the energy storage device accordingly. Such circuits are implemented, for example, as boost converters, step-up converters, or push-pull converters. The voltage converter stage eliminates the need for a series connection of cells that would otherwise be necessary to achieve the required higher voltage. Likewise, a complex charging circuit is saved to prevent deep discharge or overcharging of the secondary cells and/or supercapacitors of the energy storage device.

In embodiments where kinetic energy is used by a generator operation of the engine to charge the energy storage device, a corresponding voltage converter may also be required for this purpose, for example a buck converter. Alternatively, instead of a unidirectional voltage converter, a corresponding bidirectional converter can be used for each direction of the energy flow. In at least one embodiment, the braking device comprises a brake body configured to form a frictional connection with the motor shaft. In at least one embodiment, the braking device is arranged to reduce the speed of the rotational movement by recuperating kinetic energy.

In at least one embodiment, the locking device comprises a locking element configured to form a form-fitting connection in the locking device

DK 181088 B1 17 In at least one embodiment, the actuator system comprises a system of rotating shafts, wherein the motor shaft is part of the system of rotating shafts, and the motor is adapted to drive the rotating shafts interdependently.

In various embodiments, the control is attached to the linear actuator or forms an integrated unit with the linear actuator.

Alternatively, the control can also be arranged separately from the linear actuator.

According to the improved actuator concept, a piece of furniture with at least one adjustable component and with an actuator system according to one of the described embodiments for adjusting the component is also proposed.

Such pieces of furniture are, for example, tables, beds or adjustable seating and reclining furniture.

The improved drive concept also relates to a method for controlling an actuator system according to one of the described embodiments.

For example, the method comprises the steps of: controlling the motor, the braking device, and the locking device using the controller; and Supply the controller and the braking device with energy from the rechargeable energy storage during a braking phase.

In various embodiments of the method, the method further comprises detecting the failure of the line voltage and establishing the supply of power to the braking device from the energy storage device during the braking phase when the line voltage fails.

DK 181088 B1 18 Further embodiments of the method result directly from the various embodiments set forth in connection with the description of the actuator system and, in particular, the rechargeable energy storage device.

In the following, the improved concept is explained in detail by means of exemplary embodiments with reference to the drawings. Components which are functionally identical or have an identical effect may be given identical reference signs. Identical components or components having an identical function may be explained only with respect to the figure in which they first appear. The explanation is not necessarily repeated in subsequent figures. In the figures: Figure 1 shows an example of an electrically adjustable piece of furniture; Figure 2 shows a schematic representation of a linear actuator; Figures 3 to 8 show schematic block diagrams illustrating the energy flow in an actuator system according to the improved concept; and Figure 9 shows the exemplary temporal course of the speed of the rotational movement and that of the energy balance in an actuator system according to the improved concept.

Figure 1 shows a schematic structure of an electrically adjustable piece of furniture, which is designed as a height- adjustable table. The table has a table top 1 which can be adjusted in height by means of an actuator system, in this

DK 181088 B1 19 case a linear actuator formed by a motor arrangement 100 and a conversion arrangement 200, e.g. a spindle-nut system. The conversion arrangement 200 is arranged to convert a rotational movement generated by the motor arrangement 100 into a linear deflection or length change or elongation of the linear actuator. The linear actuator is arranged in a telescopic column 300. The motor arrangement 100 is connected to a control unit 400 through which a user can, for example, input travel commands for the table to effect a height adjustment. Additionally, the actuator system includes a rechargeable energy storage device 500 connected to the motor arrangement. Here, the energy storage device 500 is formed as a stand-alone unit. Alternatively, the rechargeable energy storage unit 500 may be integrated into the motor arrangement

100. Figure 2 shows a perspective view of a linear actuator formed by a motor assembly 100 and a spindle-nut system as an example of a translator assembly 200. The motor assembly 100 has a rotating shaft, for example a shaft from a system of rotating shafts, which is mechanically coupled to the spindle-nut system which converts the rotational movement into an elongation or linear displacement of the linear actuator. Instead of the spindle-nut system, another type of conversion arrangement 200 can be used that is coupled to the shaft and is arranged to convert a rotational movement generated by the shaft into an elongation of the linear actuator, for example based on cable pulls. The elongation of the linear actuator, i.e. its actuator action, takes place, for example, in the longitudinal direction of the motor shaft.

DK 181088 B1 20 In various embodiments, a controller or actuator controller may be integrated into the control unit 400 or separately from the control unit in its own housing or on or in the linear actuator 100.

For example, as mentioned, spindle-nut systems are used to convert rotational movement into linear motion in a linear actuator. However, when a load is applied axially to the nut of the spindle-nut system, and the load is large enough to overcome the friction present, the opposite happens and the linear motion is converted to rotational movement. This is usually an undesirable effect. Although such an effect can occur regardless of the orientation of the spindle, reverse drive most often occurs in vertical applications when a load is stopped and an external holding mechanism such as a brake or counterweight fails. For example, in conventional linear actuators and actuator systems, such an effect occurs, for example, in table furniture with vertically adjustable table tops, where the load of the table top is transferred to the actuator via a mechanism. Under certain circumstances, such an effect can also occur during transport of the table, when the table is lifted at the table top. The forces that can trigger the backward drive or a downward slide are determined, for example, by the moving parts of the table frame, such as the weight and/or inertia of these parts. It has been found that the efficiency of a linear actuator is the main indicator of whether or not a spindle will take over the reverse drive or slip. The higher the efficiency, the more likely it is that the spindle or linear actuator will

DK 181088 B1 21 slip when an axial force is applied, i.e. a force along the direction of length change. The efficiency of the linear actuator with a spindle-nut system is determined in particular by the lead angle of the spindle and the friction in the spindle-nut system. The greater the lead angle, the higher the efficiency of the spindle. This means that spindles with a higher pitch, for example 20 mm per revolution instead of 5 mm per revolution, have a higher efficiency and therefore tend to slip more. In addition to the lead angle, lubrication or a geometry of the gearing, for example, also influence the efficiency, as these affect the friction.

In various embodiments, a motor of the linear actuator may drive the conversion arrangement directly or by means of an intermediate speed reduction gear. Such a speed reduction gear may also be integrated in the motor, in which case it may be referred to as a geared motor. Such a linear actuator is self-locking if the entire chain consisting of motor, optional gearbox and conversion arrangement is self-locking, i.e. if, for example, only the spindle of a spindle-nut system is self-locking on its own, for example due to friction or the lubrication pitch angle, etc., or if the spindle is self-locking in combination with the speed reduction gearbox and/or the motor. In the case of the motor, for example, friction from carbon brushes, bearings or magnetic detent torques can influence self-locking.

High self-locking reduces the overall efficiency of the linear actuator, requiring a larger and more expensive motor.

DK 181088 B1 22 According to the improved actuator concept, it is proposed to equip a non-self-locking actuator system with a braking device and a locking device.

If an actuator, for example in a table leg, does not have self-locking and is also not locked by a locking arrangement, then the weight force of the table top would immediately accelerate the actuator downwards.

Therefore - without a locking arrangement - a torque is always required by the motor in the actuator, which is opposed to the weight force.

The force due to the torque is equal to the weight force.

The torque of the motor is proportional to a motor current, which is generated by the voltage at the motor terminals.

If, for example, a tabletop is to be lowered, the torque of the motor must first be reduced.

This causes the motor to accelerate.

However, so that the motor does not accelerate continuously but moves down at a constant speed after acceleration, the torque is increased again to such an extent that the force from the torque corresponds to the weight force.

By increasing the current and the resulting torque, the motor is finally decelerated.

An example of a mechanical braking device is described in DE 10 2020 100 439 of the applicant.

As a basic principle, such a braking device is based on a frictional locking principle which can be selectively activated and deactivated and, for example, automatically enables an increase in the self- locking of the actuator system.

According to the improved drive concept, it is further proposed to provide the linear actuator with a locking device directly or indirectly coupled to the motor shaft of the motor and adapted to selectively effect a rotational lock of the motor shaft by means of at least one locking element.

DK 181088 B1 23 An example of a locking device is described in the applicant's DE 10 2019 113 111. Due to the possibility to effect a selective rotation lock of the motor shaft, i.e. to lock the linear actuator, no self-locking drive arrangement is required to avoid slippage. As a result, less power is required from the motor, which leads to lower costs and, especially when omitting a speed reducer, also reduces the required installation space or the volume and/or weight of the linear actuator. Omitting a speed reducer also eliminates a source of unwanted noise from the linear actuator. For the operation of the actuator system, the motor arrangement 100 further comprises, in addition to, for example, the control 101, the motor 102, the braking device 103 and the rechargeable energy storage device 500, which is shown here as a separate element for better illustration but is associated with the braking arrangement, a power supply 105, which is connected to an external voltage supply 600, for example a mains voltage. According to the improved concept, the rechargeable energy storage device 500 is arranged to supply at least the control system as well as the braking device 103 with an electrical voltage, in particular in the absence or failure of the supply via the external voltage supply 600, so that a controlled braking process can be carried out and the locking device 104 can reliably activate the rotation lock. The following figures illustrate the improved concept by means of circuit sketches.

The motor 102 is a conventional DC motor, but may alternatively be a three-phase motor, such as a three-phase BLDC motor.

DK 181088 B1 24 For example, the braking device 103 produces an electrical braking effect by appropriately driving the motor 102. For example, the braking device 103 has terminals in an H-circuit comprising, for example, four switches with the motor 102 arranged therebetween, and a buffer capacitor in an intermediate circuit. In this case, the controller 101 generates the desired terminal voltage and voltage direction from the DC link voltage via appropriate PWM control of the switches of the H-circuit.

The speed of the motor 102 depends on the terminal voltage. To achieve a desired speed, the controller 101 changes the terminal voltage until the desired speed is reached. If a terminal voltage lower than 0 is required to reach a certain speed, the motor is in generator mode, i.e. the internal motor voltage is higher than the voltage across the resistor. Since the internal voltage depends on the speed, the motor is in generator mode from a certain speed and this speed is proportional to the motor resistance. This means that the lower the resistance, the lower the speed at which generator operation starts. When the motor 102 decelerates, the speed and thus the generated internal voltage decrease. The control 101 must therefore raise the terminal voltage. Once the terminal voltage becomes greater than 0, the motor 102 exits generator operation. The energy to further increase the terminal voltage now comes from the DC link voltage.

When the terminal voltage is negative, i.e. the motor 102 is in generator mode, the voltage will charge the buffer capacitor of the DC link. To avoid increasing the DC link

DK 181088 B1 25 voltage above a maximum value, for example 30 V, the energy is used to charge the rechargeable energy storage device 500. If the engine leaves generator mode, then the buffer capacitor is discharged.

The DC link voltage starts to drop, the control 101 detects this and uses the rechargeable energy storage device 500 to charge the capacitor and maintain the DC link voltage.

For example, if the rechargeable energy storage device 500 has less than 5V nominal voltage, a bidirectional voltage converter is needed between 5V and the DC link voltage.

If the mains voltage fails during motor activity, the DC link voltage can be maintained by charging the DC link buffer from the voltage generated by motor 102. Once this energy is insufficient, or no energy is generated at all, the DC link voltage begins to decrease.

The controller 101 detects this and uses the rechargeable energy storage device 500 to use it to supply energy to the buffer again.

The DC link voltage is thus available both when the mains voltage fails and when the mains voltage is present.

Braking can be performed in the same way in both cases.

Figures 3 through 8 schematically illustrate the flow of power within the actuator system in various situations.

In particular, Figure 3 shows the normal operation of the actuator system when an external power supply 600 is present.

The power supply 105 fed by the external power supply 600 supplies power to the controller 101 and the motor 102, for example, via the controller 101. For the sake of clarity, the block diagram does not explicitly show the braking device 103 and the locking device 104. For example, the braking device 103 and the locking device 104 are formed as integrated

DK 181088 B1 26 components of the control 101 and/or the motor 102. Accordingly, the braking device 103 and the locking device 104 are supplied with voltage, if necessary, via the control

101.

In Figure 3, the arrows indicate that in this situation the rechargeable energy storage device 500 is connected to and charged by the power supply 105. For example, the energy storage device 500 includes one or more secondary cells connected in parallel and/or one or more supercapacitors connected in parallel. There is no transfer of energy from the energy storage device 500 to other components of the actuator system in this constellation.

Figure 4 shows an alternative actuator system similar to the one in Figure 3, but with the difference that here the energy storage device 500 is charged directly by the external power supply 600. This is done, for example, via a stand-alone power source, such as another power supply, which is integrated into the energy storage device 500. For example, the energy storage device 500 comprises its own 5 V power supply.

Figure 5 shows the schematic power flow in an actuator system according to Figure 3 or 4, where no external power supply 600 is available. For example, the power supply 600 has failed. If this failure occurs during an adjustment of the adjustable component of the furniture and the motor shaft of the motor 102 is in motion at the time of the power failure, this is detected by the controller 101 and a controlled braking of the rotational movement of the motor shaft is initiated by the braking device 103 so that ultimately the

DK 181088 B1 27 locking device 104 can activate the rotation lock of the motor shaft. Figure 5 shows an exemplary energy flow during a first partial phase of the braking phase, the so-called recuperation phase. As long as the motor 102 or the motor shaft has a certain minimum speed, the kinetic energy in a generator mode of the motor 102 can be used to operate the control 101 and the braking device 103, for example via the control 101, by recuperation. This principle is known, for example, from the automotive industry, where this is used in vehicles with hybrid drive. Similarly, the kinetic energy of the motor 102 can be expended to charge the energy storage device 500.

Since an operating voltage of the motor 102, for example 20 V, is typically higher than the voltage required to charge the energy storage device 500, for example 5 V, a voltage converter 106 is coupled between the motor 102 and the energy storage device 500. Figure 6 shows the exemplary energy flow during a second partial phase of the braking phase, the active braking phase. As soon as the speed of the motor 102 or the motor shaft is too low to operate the control 101 and the braking device 103, this is detected by the control 101 and switched to the energy storage device 500 as an energy source. Similarly to the voltage converter 106, another voltage converter 107 converts the voltage of the energy storage device 500, for example 5 V, into the voltage required to operate the control 101 and the braking device 103. An energy capacity of the energy storage device 500 is thereby dimensioned in such a way that a controlled braking process of the rotational

DK 181088 B1 28 movement can be carried out and a speed is achieved which is not critical for the operation of the locking device 104. In particular, the energy capacity of the energy storage device 500 is not sufficient to operate the entire actuator system including the motor 102.

Figure 7 shows an alternative actuator system similar to that in Figure 5, but with the difference that here the energy for supplying the control 101 and the braking device 103 also comes from the energy storage device 500 during the first braking phase, the recuperation phase. Additionally, only during the first braking phase is the energy storage device 500 simultaneously charged by the kinetic energy of the motor

102. Instead of two unidirectional voltage converters 106, 107, a bidirectional voltage converter may alternatively be used.

Figure 8 shows a variant of the actuator system in which only the control 101 and the braking device 103 are supplied during the entire braking phase in generator mode and no charging energy is available for the energy storage device

500. In this case, the energy storage device 500 is charged only with the mains voltage of the external power supply 600 and, in the event of a mains voltage failure, supplies the energy for a switching operation that generates a motor short circuit and thus causes the rotational movement to be braked. In that case, the kinetic energy is released in the form of heat via the resistance of the motor windings.

Figure 9 shows the time curve of the speed of the rotational movement and that of the energy balance during a downward movement of a table top 1 with a subsequent braking process. The upper diagram illustrates the speed curve as a function

DK 181088 B1 29 of time, while the lower diagram shows the curve of the energy supplied to the control 101 and braking device 103. At time t=0, the table top is already moving downwards at a constant speed, which is represented in the diagram by the negative speed. At time tl, the braking process by the braking device 103 begins. At time t3, the braking process is finished and the table plate 1 is in a rest position. It can be seen from the lower diagram that between t=0 and t2 the supplied energy is negative, i.e. the motor is operating in generator mode and energy is released, for example to charge the energy storage device 500 and to supply the control 101 and the braking device 103 with sufficient voltage. If the kinetic energy of the motor 102 is no longer sufficient to supply the control 101 and the braking device 103 with sufficient voltage, i.e. the speed of the motor 102 or the motor shaft is too low, energy must be supplied from the energy storage device 500 to continue braking by the braking device 103.

In the example, after the rotational movement has been fully decelerated, just enough energy is still supplied to the controller 101 and the braking device 103 between t3 and the time t4 to hold the motor so that the locking device 104 can reliably activate the rotation lock, which may take some time and may not necessarily be instantaneous. For example, an engagement of the locking device 104 may take a few 100 ms. If the motor shaft were to start moving again during this time, this could result in the engagement process being unsuccessful. Alternatively, between t3 and t4, the motor shaft can still be slowly rotated enough to allow a locking element of the locking device 104 to engage.

DK 181088 B1 30

A linear actuator according to any of the previously described embodiments may form an actuator system together with a controller.

In addition to conventional control functions, such a controller is, for example, set up to activate, deactivate and keep deactivated the rotation lock according to the previously described procedure in order to enable continuous motor movement.

This includes, in particular, controlling the motor to move the locking element into the locking area and optionally actively jamming the locking element, and further controlling the motor to release the jamming.

Such a linear actuator or such an actuator system with such a linear actuator can be used in a variety of ways in different pieces of furniture.

In particular, such pieces of furniture can be formed by tables or other table furniture, but also by adjustable beds in which, for example, a foot part and/or a head part of the bed are adjustable.

Another application is, for example, adjustable seating and reclining furniture, such as television armchairs or the like.

DK 181088 B1 31 List of reference signs 1 table top 100 motor arrangement 101 controller 102 motor 103 braking device 104 locking device 105 power supply 106, 107 voltage transformer 200 conversion arrangement 300 telescope column 400 control unit 500 energy storage device 600 external voltage supply

Claims

DK 181088 B1 32 PATENT CLAIM

1. Actuator system, in particular for adjusting a piece of furniture, the actuator system comprising - a motor (102) having a system of rotating shafts driven interdependently by the motor; - a conversion arrangement (200) which comprises one of the rotating shafts and is arranged to convert a rotational movement of this shaft generated by the motor into an extension of the actuator system; - a locking device (104) coupled to one of the rotating shafts and adapted to selectively effect rotation locking of that shaft; and - a control unit (101) for controlling the motor (102) and the locking device (104); characterized in that - the actuator system further comprises a braking device (103) comprising at least one rechargeable energy storage device (500), which is designed to supply energy to a control unit (101) and the braking device (103) during a braking phase, and which is designed to decrease a rotational movement speed of one of the rotating shafts; and - the control unit (101) is further configured to control the brake device (103).

2. Actuator system according to claim 1, wherein the control unit (101) is configured to - control the motor (102) in a generator mode during a first partial phase of the braking phase, in which the energy storage device (500) is charged with generated braking energy; and - during another sub-phase of the braking phase, to reduce the speed of rotational movement to a value below a threshold value via the energy from the energy storage (500).

3. Actuator system according to claim 2, where the control unit (101) is further arranged to reduce the rotational movement speed via energy from the energy storage device (500) in the event of a supply voltage failure.

4. Actuator system according to claim 2 or 3, wherein the control unit (101) is further arranged to use the energy from the energy storage device (500) to change the terminal voltage of a motor during the second sub-phase to reduce the rotational movement speed.

5. Actuator system according to claim 4, wherein the control unit (101) is further arranged to reverse the motor terminal voltage.

6. Actuator system according to claim 4 or 5, wherein the control unit (101) is further arranged to continuously increase and decrease the motor terminal voltage.

7. Actuator system according to claim 2 or 3, wherein the control unit (101) is further arranged to use the energy from the energy storage device (500) to establish a connection between a braking resistor and the motor (102) during the second sub-phase.

8. Actuator system according to claim 2 or 3, wherein the braking device (103) comprises a > mechanical brake and wherein the control unit (101) is further arranged to use the energy from the energy storage device (500) to establish a frictional connection between the mechanical brake and a shaft of the actuator system during the second subphase.

9. Actuator system according to one of claims 1 to 8, wherein the control unit (101) is configured to - detect whether the rotational movement speed is higher than a threshold value; and - control the braking device (103) in such a way that the rotational movement speed is reduced to a value below the threshold value.

10. Actuator system according to one of claims 2 to 9, wherein the threshold value corresponds to a non-critical rotational movement speed of the locking device (104).

11. Actuator system according to one of claims 1 to 10, wherein the energy storage device (500)

has a voltage lower than or equal to 5 V.

12. Actuator system according to one of claims 1 to 11, wherein the energy storage device (500) comprises one, in particular a single, secondary cell.

Actuator system according to one of claims 1 to 12, wherein the energy storage device (500) comprises secondary cells connected in parallel.

Actuator system according to one of claims 1 to 13, wherein the energy storage device (500) comprises a lithium cell.

15. Actuator system according to one of claims 1 to 14, wherein the energy storage device (500) comprises a supercapacitor.

16. Actuator system according to one of claims 1 to 15, wherein the energy storage device (500) has a power capacity of less than 100 W, in particular a power capacity in the range of 10 — 20 W.

17. Actuator system according to one of claims 1 to 16, wherein the energy storage device (500) has an energy capacity which is less than an energy required to control the motor (102).

18. Actuator system according to one of claims 1 to 17, wherein the brake device (103) further comprises a voltage converter (106, 107).

19. Actuator system according to one of claims 1 to 18, wherein the locking device (104) comprises a locking element configured to form a form-fitting connection in the locking device (104).

20. Furniture with at least one adjustable component and with an actuator system according to one of claims 1 to 19 for adjusting the component.

21. A method for controlling an actuator system according to one of claims 1 to 19, wherein the method comprises - controlling the motor (102), the braking device (103) and the locking device (104) via the control unit (101); characterized in that the method further comprises:

- supplying the control unit (101) and the braking device (103) with energy from the rechargeable energy storage (500) during a braking phase.