Method for detecting a mechanical operating state of a drug delivery device

Abstract

The invention relates to a method for detecting a mechanical operating state of a drug delivery device (1), the method comprising the steps of gradually increasing a motor drive current for a motor (33) of the drug delivery device (1), measuring a position or movement of an output member (32) movable by the motor (33) by a sensor, determining a minimum motor drive current required to initially move the output member (32) from a rest state, and inferring the delivery device operating state from a development of the successively determined minimum motor drive current values.

Description

Technical Field

[0001] This invention relates to injection devices or pharmaceutical delivery devices for injecting, delivering, administering, infusing, or dispensing substances and / or liquids such as insulin, hormone preparations, or vaccines. It begins with a method for detecting the mechanical operating condition of a pharmaceutical delivery device. Background Technology

[0002] There are many diseases that require routine treatment via subcutaneous drug administration, and numerous drug delivery devices have been developed to support patients in accurately and controllably delivering a specific amount of medication during self-administration. Delivery devices include injection devices that are removed from the injection site after each medication event or drug delivery process, and infusion devices with cannulas or needles that remain in the patient's skin for extended periods.

[0003] For example, diabetes can be treated with the aid of variable-dose insulin pens via self-administration of insulin or its derivatives. Pen devices typically have an elongated device body defining a longitudinal main device axis. An automated injection device has a motor or drive spring for biasing the plunger rod and deflecting the piston in the container, where the drive spring may have to be manually loaded or tightened before the injection dose. Manually powered delivery actuators require the user to manually provide energy to move the piston, for example, by applying a distal force component to the injection device.

[0004] The dosage of medication to be injected is typically selected manually by turning the dosage knob and observing the actual dose entered from the insulin pen's dosage window or display. The dosage is dispensed by inserting a needle into the appropriate part of the skin and by manually moving the piston or pressing the release button on the auto-injection device. Auto-injection devices include an electric motor or bias drive element for automatically dispensing the set dose.

[0005] Therapies based on drug delivery devices typically benefit from electronic units or control units that are embedded or integrated into the delivery device or detachably attached to it as part of an auxiliary or supplementary electronic module or add-on device. The electronic unit monitors the drug delivery process to proactively prevent device malfunctions and / or keep track of the dose already administered, and generates data related to the instantaneous status and / or use of the delivery device. Suitable sensors in the electronic unit readily detect the status or signals from any type of indicating component (including user interface elements and actuators) of the delivery device. A wireless communication unit of the electronic unit is provided for wirelessly communicating (specifically uploading) drug information to a nearby mobile device, dedicated medical gateway, or cloud server. The drug information includes at least a timestamp and expulsion dose, indicating the time of the medication event and the amount of drug delivered. Drug information can be transmitted instantaneously or stored in a storage unit connected to a processing unit for later uploading or batch transmission.

[0006] The delivery device may include a safety mechanism adapted to identify malfunctions, defects, or errors within the delivery device, particularly malfunctions related to the fluid path of liquid drugs.

[0007] For example, EP3213785 B1 discloses a drug pump that includes an electric motor for dispensing drugs. Electronic control circuitry measures the pump motor current. If a blockage exists in the system, it can cause an increase in reservoir fluid pressure. This can result in greater motor torque and current as the motor attempts to overcome this fluid pressure to push the reservoir plunger. If the measured motor current is greater than a certain amount than the known average baseline motor current (which can be established in the absence of a blockage), it is determined that a blockage may have occurred. If there is a gearbox failure that prevents the motor from rotating, the measured current will be higher and the encoder will not increment. This is an indication of a drive system malfunction.

[0008] EP 3765125 A1 discloses a drug delivery device with an electric motor for moving a piston rod. Motor current is measured to energize the electric motor and is used as a signal for the load delivered by the motor. The current signal is processed by a control module to detect obstruction in the piston rod's advance.

[0009] WO 2011 / 044706 A1 recommends using force sensors to detect an increase in motor torque and consequently an increase in the drive system in the event of a malfunction.

[0010] Existing methods typically suffer from a considerable time delay before detecting a system error or malfunction, as it takes time for the current to increase to its maximum value or reach a predetermined threshold. To avoid this time delay, additional force or torque sensors are usually required. However, these require additional space and increase the manufacturing cost of the drug delivery device. Summary of the Invention

[0011] The purpose of this invention is to reliably monitor changes in the mechanical operating status of a drug delivery device and to provide early detection of malfunctions.

[0012] This objective is achieved by the method and drug delivery device according to the independent claim. Preferred embodiments are apparent from the dependent claims.

[0013] The method according to the invention relates to monitoring the dispensing process of liquid medication from a reservoir or cartridge in a drug delivery device. The drug delivery device preferably includes an electric motor adapted to move a movable output member (e.g., a movable element of the reservoir, a motor shaft, or a plunger rod) in a dispensing direction for dispensing liquid medication from the reservoir. The method according to the invention includes the following steps:

[0014] a) The motor drive current for the motor of the drug delivery device is gradually increased or ramped up (or ramped up) from zero or below the motor current required to move the movable output component by driving the motor used to dispense the drug.

[0015] b) The position or movement of the output component that can be moved by the motor is continuously measured by a position sensor or motion sensor;

[0016] c) Determine the minimum motor drive current (starting current) required to initially move or shift the output component from rest or stop;

[0017] d) Record (store) the minimum motor drive current and repeat steps a) to c), preferably at least five times;

[0018] e) Infer the operating status of the delivery device based on the development (progress or curve) of multiple successively (continuously) determined minimum motor drive current values.

[0019] To obtain multiple definite minimum motor drive current values, repeat steps a) through c) above.

[0020] This method allows monitoring the development, progression, or curves of multiple defined minimum motor drive current values ​​(or motor start-up current values) as a function of time or position (and therefore, the volume of distribution). The minimum drive motor current is the current required to start the motor (i.e., to initially move the output component from a non-moving steady state to a moving or driven state). During the use of the drug delivery device, this minimum motor drive current value can be a function of time. Reasons for different values ​​include, for example, friction within the device, biasing or releasing power systems within the device, different filling levels of the drug reservoir, and degradation of material properties. However, under normal operating conditions, the minimum motor drive current value does not exceed a finite range. In the event of malfunction or system failure (as described in detail below), the minimum motor drive current required to drive the motor increases significantly compared to the minimum motor drive current value under unobstructed conditions.

[0021] Typically, automated drug delivery devices with electric motors are driven in interval mode. This means the motor is driven by several short bursts, moving the plunger rod in the dispensing direction within short intervals. Therefore, the motor is driven in a stop-and-go mode. Consequently, several intervals or bursts may occur during a single dose dispensing.

[0022] According to the present invention, in steps a) to c), for each preset dose, drive interval, or burst pulse, a minimum motor drive current and preferably the corresponding time or position value are determined and recorded, and preferably stored in an electronic module or memory in the drug delivery device. This means that for multiple allocated doses or drive intervals, a continuous sequence of minimum motor drive current values ​​(the development or progression of recorded minimum drive current values) can be determined as a function of time or position (or allocated volume).

[0023] The minimum motor drive current value represents the functionality of the delivery device. Since the motor drive current is proportional to the motor force, the minimum motor drive current value indicates an increase or decrease in the motor force required to move, for example, the output component. Therefore, a change in the minimum motor drive current and consequently, a change in the motor force, can indicate a malfunction of the delivery device (a change in operating state). For example, if there is a blockage in the fluid path, if the transmission system is blocked, or if the distribution of motion is impeded in any other way, a higher minimum motor drive current is required to move the output component, or the output component may not move at all.

[0024] For example, if the absolute value of more than one of the minimum motor drive current values ​​exceeds a predetermined threshold, a notification or alarm can be issued. In another embodiment, the rate of change of the determined minimum motor drive current value can be calculated and monitored to detect device malfunction.

[0025] Compared to existing methods, the method according to the invention allows for very early and reliable detection of malfunctions or system failures. That is, unlike known monitoring systems, the motor will not only stop when the maximum drive current (maximum motor torque) is applied or when a predetermined threshold is reached. The monitoring according to the invention allows for detection of the critical minimum motor drive current (and therefore the critical motor force) at a very early stage. In other words, once the minimum motor drive current changes in a specific manner, a malfunction can be detected very reliably before the motor drive current is increased to the maximum current value.

[0026] The drug delivery device may be an electronic injection pen that includes an electric motor for moving a plunger to dispense medication. For example, it may be a reusable electronic injection pen, or it may be a patch injector that can be applied to a user's skin for the duration of the injection. Alternatively, the drug delivery device may be an infusion system, such as a conventional medical drug pump, like an insulin pump with tubing, or it may be a tubing-free drug patch pump that can be directly attached to a user's skin; both include a drive unit comprising an electric motor.

[0027] The term “injection system” or “syringe” refers to a device that is removed from the injection site after each medication event or drug delivery process, while the term “infusion system” refers to a device with a cannula or needle that remains in the patient’s skin for an extended period of time, such as several hours.

[0028] The drug delivery device preferably includes an electronic module or electronic unit, which includes a processing device or controller, such as a microcontroller or FPGA, for performing the steps described above. The electronic module preferably includes a data storage unit for storing captured data and / or sensor signal data, as well as determined or calculated data. Furthermore, the drug delivery device preferably includes a communication unit configured to transmit data between the electronic unit and external devices, such as servers, user mobile devices, or computers in medical institutions.

[0029] The operating state refers to the working condition or status of the dispensing mechanism of the delivery device. Therefore, if, for example, the output component stops moving due to obstruction, or if the driving force of the motor required to move the output component increases in an undesirable manner, the operating state changes from the normal operating state to the error state.

[0030] The device, in the form of a rotary or linear motor, is driven by a motor drive current and preferably controlled by a controller. Typically, voltage is supplied and controlled, and the motor drive current is applied according to the supplied voltage. The delivery device includes a movable output member that is actuated by a motor for rotational or linear movement. The output member is further adapted to dispense liquid medication from a reservoir. Examples of the output member are any drive component within the reservoir, such as a motor shaft, plunger rod, drive sleeve, plunger, or dispensing mechanism of the delivery device.

[0031] According to the present invention, the motor drive current starts from zero or a low value, so that the motor is not yet operating. Subsequently, the motor drive current increases gradually or continuously. Therefore, the controller increases the motor drive current until the motor starts operating and the motor output component begins to move (rotational or linear movement, depending on the motor type). The instantaneous motor drive current when the motor begins to move the output component from a stationary state is referred to herein as the minimum motor drive current. This minimum motor drive current value is captured and stored in the electronic module each time the current increases (for each dispensed dose, drive interval, or burst pulse).

[0032] In the current context, the terms “substance,” “drug,” “pharmaceutical,” or “medicinal product” will be understood to include any flowable medical preparation suitable for controlled administration via a device such as, for example, a cannula or a needle, and to include liquids, solutions, gels, or fine suspensions containing one or more medically active ingredients. A pharmaceutical preparation may be a composition containing a single active ingredient, or a premixed or co-formulated composition containing more than one active ingredient in a single container. Pharmaceutical products include drugs, such as peptides (e.g., insulin, insulin-containing drugs, GLP-1-containing drugs, or derivatives or similar preparations), proteins and hormones, active ingredients derived from or harvested from biological sources, hormone- or gene-based active ingredients, nutritional preparations, enzymes, and other substances in solid (suspension) or liquid form, as well as polysaccharides, vaccines, DNA, RNA, oligonucleotides, antibodies, or portions of antibodies, and suitable base substances, excipients, and carrier substances.

[0033] The term "distal" refers to the direction or end of a drug delivery device that carries an injection needle or cannula, while the term "proximal" refers to the opposite direction or end away from where the needle or cannula is pointing.

[0034] In a preferred embodiment, the method further includes the following step: determining the rate of change of the minimum drive current (the rate of change over multiple recorded minimum drive current values) based on the development of successively determined minimum motor drive current values, so as to determine or infer the operating state, i.e., failure.

[0035] This means that the rate of change, i.e., the derivative of the minimum drive current curve, can be calculated based on the stored minimum motor drive current value and time or position value. The determination or calculation is preferably performed by the controller of the drug delivery device.

[0036] A specific rate of change of the captured minimum drive current value can indicate a device malfunction. Monitoring the rate of change even allows for earlier detection of malfunctions. Preferably, the absolute value of the minimum motor drive current value is also monitored to reliably detect changes in the device's operating state.

[0037] The method preferably further includes the step of comparing whether the determined rate of change of the minimum drive current value exceeds a predetermined threshold (of the rate of change).

[0038] Therefore, it can be determined whether the rate of change is below, above, or within a predetermined threshold range. If the determined rate of change exceeds the threshold (e.g., above, below, or beyond the threshold range), the controller can send a message or alarm to the user, or trigger further actions.

[0039] During the allocation period, the controller preferably analyzes the sequence of successively determined minimum motor drive current values. This means that the progression or curve of multiple minimum drive current values ​​is analyzed. This allows for efficient comparison of the determined minimum motor drive current values ​​and their progression over a period of time or within the stroke of the movable output member (e.g., during the allocation process). Therefore, continuous monitoring of the minimum motor drive current during the allocation process is possible.

[0040] If the minimum motor drive current exceeds a threshold within a specific time period (within a time range) or within a specific stroke, it can be inferred that the delivery device is not functioning properly. Periodically analyzing the captured minimum motor drive current value within a predetermined time period or within a predetermined stroke length or stroke path allows for reliable detection of malfunctions or system failures in the early stages of motor operation.

[0041] The sequence of minimum motor drive current values ​​in signal form is preferably processed by an analog or digital filter. The filtered signal has a smooth progression, and noise can be effectively removed by the filter. Therefore, signal filtering allows for reliable signal analysis and easier further processing.

[0042] The filter used is preferably a digital finite impulse response (FIR) filter. An advantage of FIR filters is that they are inherently stable because the output of an FIR filter is the sum of a finite number of finite multiples of the filter's input values. Compared to other types of filters, FIR filters use only the input values ​​and do not use previous samples of the output signal.

[0043] Preferably, the minimum motor drive current determined according to steps a) to c) above is recorded only at the beginning or the first time before dispensing the preset dose. Therefore, the minimum motor drive current is recorded each time the controller gradually increases the motor current to begin dispensing the dose. However, the minimum drive current is preferably recorded only at the first increment step, and for subsequent increment steps (several drive intervals or burst pulses during dose dispensing), the minimum motor drive current value is not recorded because these subsequent values ​​may be affected by transient phase, as the power system may be biased after several drive intervals or burst pulses.

[0044] Alternatively, the minimum drive current value of subsequent amplification steps is also recorded and can be used for a second control threshold. This means that the recorded minimum motor drive current value of subsequent amplification steps can be compared with a second and different (e.g., higher) threshold relative to the aforementioned first threshold. In this way, additional conditions during distribution, such as the behavior or progression of forces within the transmission system of the distribution mechanism, can be monitored.

[0045] As is well known, motor torque is directly proportional to the winding current in the motor. Therefore, the instantaneous driving force, or motor torque, can be periodically determined and recorded based on the instantaneous driving current. Since each minimum motor driving current value is recorded, the progression of the motor torque value as a function of time or the travel path can be determined. Therefore, the method according to the invention allows for the accurate determination of motor torque without the need for a separate, expensive, and bulky force sensor.

[0046] The progression of the drive current as a function of time or stroke preferably has a ramp shape. This means that the motor drive current gradually and linearly increases from an initial zero value or initial current value to a captured minimum motor drive current. In this way, the minimum motor drive current can be determined efficiently.

[0047] Alternatively, the motor drive current increases non-linearly or exponentially.

[0048] Once the minimum motor drive current is determined, the controller preferably switches from the increased mode to the normal drive mode, which means driving the motor with a predetermined or normal drive current to move the motor output component at a constant speed. The motor is preferably a stepper motor. In this case, the normal drive mode includes driving the motor in full-step, half-step, or micro-step modes, preferably without using any sensors or feedback signals. Therefore, after the aforementioned increased procedure, the stepper motor is driven in its normal stepping mode.

[0049] Preferably, the electric motor is a rotary motor, and the output component is a rotary motor shaft. The movement and position of the motor shaft are easily measured (e.g., using a motion sensor, position sensor, or accelerometer).

[0050] Preferably, the drug delivery device includes a motor encoder adapted to measure the movement of the motor output component. The encoder signal can be used during a period when the motor drive current gradually increases to detect the initial movement of the motor output component. Depending on the type of motor, a linear or rotary encoder can be used.

[0051] Alternatively, another position or motion sensor in the drug delivery device, suitable for measuring motion in the drive system, can be used.

[0052] The drug delivery device preferably includes a computer-readable medium for storing a computer program comprising instructions that, when executed by a computing device of the drug delivery device, cause the computing device to perform the methods described above. The computing device may be a controller, an FPGA, a microprocessor, or control circuitry within the electronic module of the drug delivery device.

[0053] The drug delivery device preferably includes a plunger for dispensing liquid drugs from a reservoir, a motor for moving the plunger, a computing device, and a computer-readable medium.

[0054] In a preferred embodiment, the drug delivery device is an injection device, particularly an injection pen. The injection device preferably includes a reservoir unit or reservoir holder (which includes a reservoir containing liquid drug) and a drive unit including a motor.

[0055] Injection devices can be disposable, reusable, or semi-disposable. The latter typically includes a disposable reservoir unit that can be replaced and discarded after injection or when the reservoir is empty. Subsequently, a new reservoir unit can be attached to a reusable drive unit to prepare the device for a new injection.

[0056] Alternatively, as mentioned above, the drug delivery device may be an infusion device such as a conventional drug pump or patch pump. Attached Figure Description

[0057] The subject matter of the present invention will be explained in more detail below with reference to preferred exemplary embodiments illustrated in the accompanying drawings, wherein:

[0058] Figure 1 A side view of a drug delivery device in the form of an electronic injection pen according to a first embodiment of the present invention is depicted;

[0059] Figure 2 Depicting Figure 1 A cross-sectional view of the injection pen;

[0060] Figure 3 A perspective view of a drug delivery device in the form of a patch syringe according to a second embodiment is depicted;

[0061] Figure 4 Depicting Figure 3 A cross-sectional view of the patch syringe;

[0062] Figure 5 A graph depicting the pull-in torque of existing delivery devices;

[0063] Figure 6 A graph depicting the pull-in torque of the filtered signal according to the present invention is provided.

[0064] The reference symbols used in the accompanying drawings and their main meanings are listed in summary form in the list of reference numerals. In principle, the same parts have the same reference symbols in the accompanying drawings. Detailed Implementation

[0065] In this specification, the term "far side" refers to the side where the pointer is attached. This is in Figure 1 and Figure 2 On the left-hand side of the upper arm. The term "proximal" refers to the opposite side, and... Figure 1 and Figure 2 On the right side of the middle.

[0066] Figure 1 and Figure 2 A drug delivery device according to a first embodiment of the present invention is shown. The delivery device is a semi-disposable electronic injection pen 1. The pen 1 includes a disposable component 2 and a reusable component 3. Figure 2 As shown in the image.

[0067] Figure 2 Depicting Figure 1 A cross-sectional view of the injection pen 1. The disposable component 2 is formed of a cartridge unit 2 (or reservoir unit), which includes a reservoir holder or cartridge holder 4 and a reservoir in the form of a cartridge 5 containing liquid medication. The cartridge unit 2 can be releasably attached to the reusable component 3.

[0068] The reusable component 3 includes an automatic drive unit 30 and a display 31. The automatic drive unit 30 includes an electric motor 33 in the form of a stepper motor for moving the plunger rod 20, a sleeve-shaped automatic drive member 34, a gear 35 connecting the motor shaft 32 of the motor 33 to the automatic drive member 34, a printed circuit board (PCB) 36 with a controller (in the form of a microcontroller or FPGA, not shown) for controlling the electric motor 33, an energy source in the form of a rechargeable battery, a data storage module, a communication module, and an encoder (all not shown) for sensing the movement of the motor shaft 32 and thus the movement of the plunger rod 20. The reusable component also includes a spring and a dosage knob 40.

[0069] The cartridge unit 2 includes an interface housing 21, a cartridge holder 4, a cartridge 5, a mechanical holder 22, and a plunger rod 20, the plunger rod having a flange 23 pivotally mounted on the distal end of the plunger rod 20. A pen cap 7 can be mounted on a needle assembly (not shown) that can be attached to the distal end of the cartridge holder 4.

[0070] If the motor 33 of the injection pen 1 is activated, for example, by the user via the dosage knob, the motor shaft 32 rotates, and the rotational movement is transmitted via gear 35 to the automatic drive member 34. The latter is splined to the plunger rod 20 and thus rotates the plunger rod 20. When the plunger rod 20 is screwed into the mechanical retainer 22 of the injection pen 1 and moves in the distal dispensing direction, the piston 9 inside the cartridge 5 moves in the dispensing direction, causing the liquid medication to be dispensed from the cartridge 5.

[0071] Figure 3 and Figure 4 Another embodiment of the invention is shown. In this second embodiment, the drug delivery device is a patch pump 100, which is adapted to be attached to the user's skin for an extended period of time. Figure 4A cross-sectional view is depicted, in which a portion of the housing is not shown. The patch pump 100 includes a drive mechanism with an electric motor 110, a motor encoder, and a controller (not shown). The motor rotates a piston 111, which in turn moves a hollow plunger rod 113 with a flange 114 in the dispensing direction to dispense liquid medication from a reservoir 112.

[0072] The method according to the present invention can be applied to... Figures 1 to 4 The delivery devices shown in the first and second embodiments can also be applied to any other electronic delivery devices including electric motors, such as conventional drug pumps, patch syringes, or fully reusable injection pens.

[0073] In the following text, regarding Figure 5 and Figure 6 Describes the control and drive of the motor in the delivery device, as well as the monitoring of the motor start-up drive current (motor input current) and the corresponding motor pull-in torque.

[0074] Figure 5 A graph depicting the pull-in torque or starting torque of a stepper motor as a function of time is presented. Therefore, the horizontal axis of the graph represents the time line, while the vertical axis represents the pull-in torque of the motor.

[0075] Line 50 in the graph marks the maximum possible pull torque of the motor with the maximum motor starting drive current. Line 52 depicts multiple pull torques recorded during normal use under normal and unobstructed operating conditions. Dashed line 51 represents the pull torque recorded under system failure conditions. That is, starting from time point t1, a blockage occurs in the fluid path, or the distribution of fluid from the reservoir is affected in any other way, requiring a higher motor torque to move the plunger rod or drive component.

[0076] According to existing technical methods ( Figure 5 The controller receives a signal from the force sensor and accordingly increases the drive current to increase the motor torque. In this way, the minimum motor drive current (or motor starting current) rises until it reaches a maximum value or threshold, and thus the maximum pull torque, as depicted by line 50. At the maximum value "m.max" or threshold, the controller stops the motor and notifies or alarms the user. Therefore, existing methods typically rely on force sensors in the delivery device to detect system malfunctions.

[0077] In the following text, regarding Figure 6 The invention describes the driving of a motor according to the present invention, as well as the monitoring of minimum drive current and pull-in torque. Figure 6 It shows the relationship with Figure 5The same traction torque curve is used, but the graph also includes curve 53, which represents the filtered signal of the minimum drive current value captured, as described in detail below.

[0078] To initiate the distribution process, the controller applies voltage, and a corresponding current is supplied to the motor. This starting current is below the minimum drive current required to initially move the motor shaft. The input drive is monitored by the controller or measured periodically, for example, by means of a shunt resistor. The rotation and position of the motor shaft are measured by a motor encoder, which has a resolution configured to detect minute movements. In particular, the motor encoder is adapted to detect the smallest possible motor step size.

[0079] The controller gradually and linearly increases the drive current. Therefore, the current supplied to the motor increases. Once the encoder detects rotational movement of the motor shaft, the controller records the actual or instantaneously measured drive current, referred to here as the minimum drive current. The controller then switches from the increased mode to a normal stepper drive mode (e.g., full-step, half-step, or micro-step mode) to drive the motor at predetermined drive intervals or burst pulses.

[0080] The determination of the minimum drive current described above is repeated at the start of each dose dispensing. Alternatively, the procedure may be repeated several times during dose dispensing (e.g., once for each burst pulse during the dispensing process). The captured and recorded minimum drive current values ​​are stored in the pen's memory. The sequence of consecutive minimum drive current values ​​is filtered by an FIR filter to reduce noise and establish a smooth progression of the data signal.

[0081] The filtered signal is described as Figure 6 Curve 53 in the figure. The length of the filter window of the FIR filter is also... Figure 6 The indicator is shown in Figure 53. Curve 53 is smooth and has reduced noise. Based on the filtered and processed signal, the controller periodically calculates the rate of change of the minimum drive current value (calculates the derivative). Alternatively, the derivative of the signal is provided by a filter. The controller compares the calculated rate of change with a predetermined threshold. The threshold is selected such that a rate of change exceeding the threshold reliably indicates a failure or system malfunction. This means that a failure such as a blockage is reliably detected if the minimum drive current value and the corresponding pull torque (known to be proportional to the input current) increase in a specific manner.

[0082] like Figure 6As depicted, after time point t1, following the first occurrence of a blockage (or any other failure) at time point t1, the curve of the determined minimum drive current increases. That is, if a threshold for the rate of change is exceeded within a given time range or travel path, the controller is able to detect the failure at time t2 (see filter window) and at the level of “ml”. This is well before time t3, at which time existing methods are able to detect the fault (reaching the maximum value “m.max”).

[0083] If the calculated rate of change of the minimum drive current exceeds a threshold, the controller stops driving the motor and sends a notification to the display of the delivery device or to an external user device via the communication unit. Additional steps may be initiated depending on the configuration.

[0084] In addition to monitoring the rate of change, the controller monitors the absolute value of the determined minimum drive current in the second control loop. The controller also sends a notification if the absolute value exceeds a threshold within a defined time period.

[0085] In addition to calculating the rate of change, the controller also periodically determines the pull-in torque based on the minimum drive current and records and stores the pull-in torque value. Information about the actual pull-in torque indicates the current operating status of the injection system. Therefore, by monitoring the minimum drive current value, instantaneous force can be determined without a force sensor.

[0086] Although the invention has been described in detail in the accompanying drawings and the foregoing description, such description is intended to be illustrative or exemplary, not restrictive. By studying the drawings, the disclosure, and the appended claims, those skilled in the art will understand and implement variations of the disclosed embodiments in practicing the claimed invention. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The fact that certain elements or steps are recited in different claims does not indicate that combinations of such elements or steps cannot be used advantageously; specifically, any further meaningful combination of claims, in addition to actual claim dependencies, should be considered disclosed.

[0087] List of reference numerals

[0088] 1. Injection pen

[0089] 2 Disposable components

[0090] 3 Reusable components

[0091] 4. Cartridge Holder

[0092] 5 medicine cartridges

[0093] 7 hats

[0094] 9 Pistons

[0095] 20 Plunger Rod

[0096] 21 Interface Housing

[0097] 22 Mechanical retainer

[0098] 23 Flange

[0099] 30 Automatic Drive Units

[0100] 31 Monitors

[0101] 32 motor shaft

[0102] 33 Electric motor

[0103] 34 Automatic drive components

[0104] 35 gears

[0105] 36 PCB

[0106] 40 Dosage knob

[0107] 100 Patch Pump

[0108] 110 motor

[0109] 111 Plunger

[0110] 112 Storage

[0111] 113 Piston rod

[0112] 114 Flange.

Claims

1. A method for detecting the mechanical operating status of a drug delivery device (1), the method comprising the following steps: a) Gradually increase the motor drive current of the motor (33) used in the drug delivery device (1); b) The position or movement of the output member (32) that can be moved by the motor (33) is measured by a sensor; c) Determine the minimum motor drive current required to initially move the output component (32) from a stationary state; d) Record the determined minimum motor drive current and repeat steps a) to c); e) Based on the development of the successively determined minimum motor drive current value, the operating status of the delivery device is inferred.

2. The method of claim 1, further comprising the step of determining a rate of change based on the development of the successively determined minimum motor drive current values ​​to infer the operating state of the delivery device.

3. The method of claim 2, further comprising the step of comparing whether the rate of change exceeds a predetermined threshold.

4. The method according to any one of claims 1 to 3, wherein, The sequence of successively determined minimum motor drive current values ​​is analyzed during repeated steps a) to c).

5. The method according to claim 4, wherein, The sequence is filtered by a filter.

6. The method according to claim 5, wherein, The filter is a finite impulse response filter.

7. The method according to claim 1 or 2, wherein, The minimum motor drive current determined according to steps a) to c) is recorded only when the output member (32) begins to move a predetermined stroke.

8. The method according to claim 1 or 2, wherein, The driving force of the motor (33) is periodically determined and recorded based on the determined minimum motor drive current.

9. The method according to claim 1 or 2, wherein, The motor drive current increases linearly until the output component (32) begins to move.

10. The method according to claim 1 or 2, wherein, The motor (33) is a stepper motor, and wherein the motor is driven in step mode without a sensor signal after the minimum motor drive current is determined.

11. The method according to claim 1 or 2, wherein, The output component (32) is a motor shaft.

12. The method according to claim 1 or 2, wherein, The position or movement is measured by a motor encoder.

13. A computer program comprising instructions that, when executed by a computing device, cause the computing device to perform the method according to any one of claims 1 to 12.

14. A drug delivery device (1) comprising a plunger rod (20) for dispensing liquid drug from a reservoir (5), a motor (33) for moving the plunger rod (20), and a computer-readable medium storing a computer program according to claim 13.

15. The drug delivery device (1) according to claim 14, wherein, The device in question is an injection device.

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