How to detect a stall condition in a rotating stepper motor

Abstract

1. A method for detecting a stall condition of a rotating stepper motor, the method comprising: measuring a back electromotive force of the stepper motor while the stepper motor is rotating; calculating a first spread of the back electromotive force, the first spread being defined by a difference between a maximum back electromotive force value and a minimum back electromotive force value in a first variation of the back electromotive force while the stepper motor is rotating; calculating a second spread of the back electromotive force, the second spread being defined by a difference between a maximum back electromotive force value and a minimum back electromotive force value in the second variation of the back electromotive force while the stepper motor is rotating; comparing the second spread to the first spread; and determining that the stepper motor is stalled when a difference between the second spread and the first spread is greater than a first predetermined value.

Description

[Technical Field]

[0001] The present invention relates to a method for detecting a stall condition in a rotating stepper motor, and in particular to a method that includes the step of measuring back EMF values. [Background technology]

[0002] Drug delivery devices such as manual injector pens or auto-injectors are commonly known for self-administration of medication by patients without formal medical training. For example, a patient suffering from diabetes may require multiple injections of insulin, or a patient may require regular injections of other types of medication, such as growth hormone.

[0003] It is advantageous if a drug delivery device for self-administration has automatic functions, as this allows the user to use the drug delivery device easily and properly, even if the user does not have specialized training or in an emergency situation.

[0004] Sensorless stall / step loss detection in stepper motor-based systems is required in various systems because stepper motors are often used to precisely control rotation angle and speed. Particularly in the case of a stepper motor for driving a plunger rod in a medication delivery device, the position of the plunger rod can be determined based on calculations of the stepper motor's rotation. Because the plunger rod position is typically used to determine information such as the amount of delivered dose / remaining dose, the accuracy of plunger rod position detection is important for dose accuracy. Therefore, detecting whether a stepper motor is stalled can improve plunger rod position detection in a stepper motor-based sensorless system and prevent motor damage. A stall condition can occur due to several factors, such as a short pulse signal period or a heavy load on the stepper motor.

[0005] Some common methods of stall detection extract the electromotive force (EMF) from a de-energizing coil and use a threshold of the back EMF to detect stall or step loss. The threshold can be dynamically derived based on rotational speed or statically fixed or calibrated for a given system. However, the threshold used must be chosen very generally, with a safety margin that accounts for various complex factors such as motor winding temperature, battery condition, and the motor's individual characteristics and tolerances. Therefore, the safety margin to prevent stall may need to be so large that the maximum available torque is significantly reduced.

[0006] Many of the devices on the market, like those mentioned above, have their advantages, but there is still room for improvement. Summary of the Invention

[0007] The invention is defined by the appended claims, to which reference should be made below.

[0008] In the present disclosure, when the term "distal direction" is used, it refers to the direction away from the dose delivery site during use of the drug delivery device. When the term "distal portion / distal end" is used, it refers to the portion / end of the delivery device, or a portion / end of a member thereof, that is located furthest from the dose delivery site during use of the drug delivery device. Correspondingly, when the term "proximal direction" is used, it refers to the direction towards the dose delivery site during use of the drug delivery device. When the term "proximal portion / proximal end" is used, it refers to the portion / end of the delivery device, or a portion / end of a member thereof, that is located closest to the dose delivery site during use of the drug delivery device.

[0009] Additionally, the terms "longitudinal," "longitudinally," "axially," or "axial" refer to a direction extending from the proximal end to the distal end, typically along a device or component thereof, in the direction of the longest extension of the device and / or component.

[0010] Similarly, the terms "transverse," "transversal," and "transversally" refer to a direction generally perpendicular to the longitudinal direction.

[0011] Additionally, the terms "circumference," "circumferential," or "circumferentially" refer to the circumference or direction of circumference relative to an axis, typically a central axis extending in the direction of greatest extension of the device and / or component. Similarly, "radial" or "radially" refers to a direction extending radially relative to an axis, and "rotation," "rotational," and "rotationally" refer to rotation relative to an axis.

[0012] Accordingly, there is provided a method for detecting a stall condition of a rotating stepper motor, the method comprising, in the following order: measuring a back EMF value of the rotating stepper motor; calculating a first spread of back EMF values, the first spread of back EMF values ​​being defined by a difference between a maximum back EMF value and a minimum back EMF value in a first variation of the back EMF values ​​as the stepper motor rotates; calculating a second spread of back EMF values, the second spread of back EMF values ​​being defined by a difference between a maximum back EMF value and a minimum back EMF value in the second variation of the back EMF values ​​as the stepper motor rotates; comparing the second spread to the first spread; and determining that the stepper motor is stalled when the difference between the second spread and the first spread is greater than a first predetermined value.

[0013] In a preferred example, a method for detecting a stall condition of a stepper motor during rotation of a medication delivery device.

[0014] Preferably, according to another embodiment, the step of measuring the back electromotive force value of the rotating stepping motor includes the steps of: The method further includes the steps of recording the back electromotive force value, and starting to calculate the first spread and the second spread only when the recorded back electromotive force value is lower than a second predetermined value.

[0015] Preferably, according to another embodiment, the second predetermined value is defined by the following steps: acquiring a rotational speed of the stepping motor; and determining the second predetermined value by searching data from a first predetermined table using the acquired rotational speed of the stepping motor.

[0016] Preferably, according to another embodiment, the step of obtaining the rotational speed of the stepper motor includes the step of measuring the rotational speed of the stepper motor.

[0017] Alternatively, according to another embodiment, obtaining the rotational speed of the stepper motor comprises receiving a signal comprising a predetermined rotational speed of the stepper motor.

[0018] Preferably, according to another embodiment, the method further comprises, in the following order, measuring a back EMF value of the stepper motor during rotation, comparing the measured value with a third predetermined value, and determining a value of the load of the stepper motor, which steps in this order can be performed before or after any step described in any one of the previous paragraphs.

[0019] Preferably, according to another embodiment, before the step of determining the value of the load of the stepping motor, the method includes the steps of acquiring a rotational speed of the stepping motor and determining a third predetermined value by searching data from a second predetermined table using the acquired rotational speed of the stepping motor.

[0020] Preferably, according to another embodiment, the above-mentioned method is adapted to be executed by a processor of a drive unit of a medication delivery device, the drive unit comprising a stepper motor.

[0021] Preferably, according to another embodiment, the drive unit comprises a stepper motor, a plunger rod operably connected to the stepper motor, and the above-mentioned processor, the processor being electrically connected to the stepper motor, and the plunger rod being configured to be driven by the stepper motor when the stepper motor is rotating.

[0022] Preferably, according to another embodiment, the processor is configured to stop, slow down, or resume rotation of the stepper motor when the processor determines that the stepper motor has stalled.

[0023] Preferably, according to another embodiment, the processor is configured to determine the position of the plunger rod based on detecting rotation of the stepper motor.

[0024] Preferably, according to another embodiment, the drive unit comprises a housing configured to receive a cassette releasably attached to the housing, the plunger rod being configured to move into a drug container in the cassette.

[0025] Preferably, according to another embodiment, the drive unit comprises a switch movable between an inactive position, in which both the processor and the motor are deactivated, and an active position, in which the processor is activated.

[0026] Preferably, according to another embodiment, the switch is configured to move from an inactive position to an active position when the cassette is attached to the housing.

[0027] Preferably, according to another embodiment, the plunger rod is connected to a stepper motor via a lead screw.

[0028] Preferably, according to another embodiment, a stepper motor is rotatable within the housing about a lead screw. The stepper motor engages the lead screw via a threaded engagement. A switch is disposed within the housing. Upon actuation of the switch, rotation of the stepper motor about the lead screw is configured to move the lead screw proximally, thereby moving a stopper of a drug container within the cassette with the lead screw.

[0029] Preferably, according to another embodiment, the stepper motor is a stepper motor.

[0030] Preferably, according to another embodiment, the motor includes a rotor and a channel extending through the rotor, with the lead screw positioned partially within the channel.

[0031] Preferably, according to another embodiment, the channel includes a thread extending around the periphery of the channel, the thread engaging the thread of the lead screw.

[0032] Alternatively, according to another embodiment, the drive unit comprises a connector operatively connected to the rotor, such that the connector is configured to be rotated by the rotor.

[0033] Preferably, according to another embodiment, the channel extends through the connector and is aligned along the longitudinal axis with the channel of the rotor.

[0034] Preferably, according to another embodiment, the channel of the connector includes threads extending around the periphery of the channel of the connector, the threads engaging the threads of the lead screw.

[0035] Preferably, according to another embodiment, the connector is attached to the rotor.

[0036] Preferably, according to another embodiment, the connector and the rotor are made of different materials.

[0037] Preferably, according to another embodiment, the connector is made of plastic.

[0038] Preferably, according to another embodiment, the rotor is made of metal.

[0039] Preferably, according to another embodiment, the longitudinal axis is the central axis of the motor.

[0040] Preferably, according to another embodiment, the engagement formed between the plunger and the inner wall of the housing is a rib-rib or rib-groove engagement.

[0041] Preferably, according to another embodiment, the engagement formed between the lead screw and the inner wall of the housing is a rib-rib or rib-groove engagement.

[0042] Preferably, according to another embodiment, the distal end of the lead screw includes a polygonal cross-section perpendicular to the longitudinal axis, and the inner wall of the housing includes a polygonal cross-section perpendicular to the longitudinal axis.

[0043] Preferably, according to another embodiment, the stepper motor is configured to reciprocate the movement of the lead screw.

[0044] Preferably, according to another embodiment, the drive unit comprises a second switch accommodated within the housing.

[0045] Preferably, according to another embodiment, the second switch is aligned with the distal end of the lead screw in the direction of the longitudinal axis.

[0046] Preferably, according to another embodiment, the second switch is positioned distally away from the distal end of the lead screw.

[0047] Preferably, according to another embodiment, the second switch is configured to be toggled by the distal end of the lead screw when the lead screw is moved distally relative to the stepper motor, such that the motor is stopped when the second switch is toggled.

[0048] Preferably, according to another embodiment, the second switch is a contactless switch.

[0049] Alternatively, according to another embodiment, the second switch is configured to be toggled by being pushed distally relative to the housing by the distal end of the lead screw.

[0050] Preferably, according to another embodiment, the second switch comprises a flip arm.

[0051] Preferably, according to another embodiment, the second switch is configured to be toggled when the flip arm is pivoted by the distal end of the lead screw.

[0052] Preferably, according to another embodiment, the housing extends along a longitudinal axis between a proximal end and a distal end.

[0053] Preferably, according to another embodiment, the housing includes a fastener at a proximal portion of the housing.

[0054] Preferably, according to another embodiment, the fastener is configured to be releasably attached to a counter fastener of a cassette of a medication delivery device.

[0055] Preferably, according to another embodiment, the fastener and the counter-fastener form a bayonet or thread connection.

[0056] Preferably, according to another embodiment, the switch is a contactless switch.

[0057] Preferably, according to another embodiment, the drive unit comprises a communication unit.

[0058] Preferably, according to another embodiment, the communication unit is adapted to receive information from the cassette.

[0059] Preferably, according to another embodiment, the communication unit is adapted to be activated when the switch is in the activated position.

[0060] Preferably, according to another embodiment, the switch is a contactless switch.

[0061] Alternatively, according to another embodiment, the switch is operably movable between an actuated position in which the switch is activated and an inactuated position in which the switch is deactivated by components of the cassette of the medication delivery device when the cassette is attached to the housing.

[0062] Preferably, according to another embodiment, the drug container of the drug delivery device is a syringe, a cartridge or a collapsible bag.

[0063] Preferably, according to another embodiment, the drug container of the drug delivery device is made of glass or plastic material.

[0064] Preferably, according to another embodiment, the drug container of the drug delivery device is housed in a cassette.

[0065] Preferably, according to another embodiment, the drug delivery device is an injection device, an inhalation device, or a medical spray.

[0066] Preferably, according to another embodiment, the injection device is configured to perform subcutaneous, intramuscular or intravenous injections.

[0067] Preferably, according to another embodiment, the medication delivery device is an auto-injector.

[0068] Preferably, according to another embodiment, the drug delivery member is a syringe needle or a spray nozzle.

[0069] Preferably, according to another embodiment, the drug delivery member is housed in a cassette.

[0070] Preferably, according to another embodiment, the cassette is configured to be completely received within the housing of the drive unit.

[0071] Preferably, according to another embodiment, the cassette is configured to be partially received within a housing of the drive unit.

[0072] Preferably, according to another embodiment, the cassette comprises an information carrier.

[0073] Preferably, according to another embodiment, the information tag is one of an RFID chip, an NFC chip, a barcode, and a QR code.

[0074] Preferably, according to another embodiment, the information carrier is attached to the outer surface of the body of the cassette.

[0075] Preferably, according to another embodiment, the information carrier is embedded in the body.

[0076] Preferably, according to another embodiment, the information carrier is attached to the medication container.

[0077] Preferably, according to another embodiment, the information carrier is a flexible sheet.

[0078] Preferably, according to another embodiment, the body has a counter-fixture releasably attached to a fixation of the housing of the drive unit, and a delivery member cover.

[0079] Preferably, according to another embodiment, the body extends along an axis between a proximal end and a distal end.

[0080] Preferably, according to another embodiment, the delivery member cover is telescoping relative to the proximal end of the body between an extended position in which the delivery member cover projects axially from the proximal end of the body, and a retracted position.

[0081] The drug delivery devices described herein can be used to treat and / or prevent one or more of many different types of disorders. Exemplary disorders include, but are not limited to, rheumatoid arthritis, inflammatory bowel disease (e.g., Crohn's disease and ulcerative colitis), hypercholesterolemia, diabetes (e.g., type 2 diabetes), psoriasis, migraines, multiple sclerosis, anemia, lupus, atopic dermatitis, asthma, nasal polyps, acute hypoglycemia, obesity, anaphylaxis, and allergies. Exemplary drug types that can be included in the drug delivery devices described herein include, but are not limited to, small molecules, hormones, cytokines, blood products, antibodies, antibody-drug conjugates, bispecific antibodies, proteins, fusion proteins, peptibodies, polypeptides, pegylated proteins, protein fragments, protein analogs, protein variants, protein precursors, chimeric antigen receptor T-cell therapy, cell or gene therapy, oncolytic viruses, or immunotherapies and / or protein derivatives.Exemplary drugs that may be included in the drug delivery devices described herein include etanercept (rheumatoid arthritis, inflammatory bowel disease (e.g., Crohn's disease and ulcerative colitis)), evolocumab (hypercholesterolemia), exenatide (type 2 diabetes), secukinumab (psoriasis), erenumab (migraine), alirocumab (rheumatoid arthritis), methotrexate (amethopterin) (rheumatoid arthritis), tocilizumab (rheumatoid arthritis), interferon beta-1a (multiple sclerosis), and steroids. inflammatory bowel disease), sumatriptan (migraine), adalimumab (rheumatoid arthritis), darbepoetin alfa (anemia), belimumab (lupus), peginterferon beta-1a' (multiple sclerosis), sarilumab (rheumatoid arthritis), semaglutide (type 2 diabetes, obesity), dupilumab (atopic dermatitis, asthma, nasal polyps, allergies), glucagon (acute hypoglycemia), epinephrine (anaphylaxis), insulin (diabetes), atropine and vedolizumab (inflammatory bowel disease) Diseases (e.g., Crohn's disease and ulcerative colitis), ipilimumab, nivolumab, pembrolizumab, atezolizumab, durvalumab, avelumab, cemiplimab, rituximab, trastuzumab, ado-trastuzumab emtansine, fam-trastuzumab deruxtecan-nxki, pertuzumab, transtuzumab-pertuzumab, alemtuzumab, belantamab-mafodotin-blmf, bevacizumab, blinatumomab, brentuximab vedotin , cetuximab, daratumumab, elotuzumab, gemtuzumab ozogamicin, 90-yttrium-ibritumomab tiuxetan, isatuximab, mogamulizumab, moxetumomab pasudotox, obinutuzumab, ofatumumab, olaratumumab, panitumumab, polatuzumab vedotin, ramucirumab, sacituzumab govitecan, tafasitamab, or margetuximab (non-limiting examples of associated disorders are in parentheses). Pharmaceutical formulations comprising any of the drugs described herein, for example, a pharmaceutical formulation comprising a drug listed herein (or a pharmaceutically acceptable salt of the drug) and a pharmaceutically acceptable carrier, are also contemplated for use in the drug delivery devices described herein.Pharmaceutical formulations containing the drugs listed herein (or pharmaceutically acceptable salts of the drugs) may contain one or more other active ingredients, or may be the only active ingredient present.

[0082] Exemplary drugs that may be included in the drug delivery devices described herein include, but are not limited to, immuno-oncology or bio-oncology agents such as immune checkpoints, cytokines, chemokines, differentiation clusters, interleukins, integrins, growth factors, enzymes, signaling proteins, pro-apoptotic proteins, anti-apoptotic proteins, T cell receptors, B cell receptors, or costimulatory proteins.

[0083] Exemplary drugs that may be included in the drug delivery devices described herein include HER-2 receptor modulators, interleukin modulators, interferon modulators, CD38 modulators, CD22 modulators, CCR4 modulators, VEGF modulators, EGFR modulators, CD79b modulators, Trop-2 modulators, CD52 modulators, BCMA modulators, PDGFRA modulators, SLAMF7 modulators, PD-1 / PD-L1 inhibitors / modulators, B lymphocyte antigen CD19 inhibitors, B lymphocyte antigen CD20 modulators, CD3 modulators, CTLA-4 inhibitors, TIM-3 modulators , VISTA modulators, INDO inhibitors, LAG3 (CD223) antagonists, CD276 antigen modulators, CD47 antagonists, CD30 modulators, CD73 modulators, CD66 modulators, CDw137 agonists, CD158 modulators, CD27 modulators, CD58 modulators, CD80 modulators, CD33 modulators, APRIL receptor modulators, HLA antigen modulators, EGFR modulators, B lymphocyte cell adhesion molecule modulators, CDw123 modulators, Erbb2 tyrosine kinase receptor modulators, mesothelin modulators, HAVCR2 antagonists, NY-ESO-1 OX40 receptor agonist modulators, adenosine A2 receptors, ICOS modulators, CD40 modulators, TIL therapy or TCR therapy.

[0084] Exemplary drugs that may be included in the drug delivery devices described herein include AC, high-dose AC, TCH, GT, EC, TAC, TC, TCHP, CMF, FOLFOX, mFOLFOX6, mFOLFOX7, FOLFCIS, CapeOx, FLOT, DCF, FOLFIRI, FOLFIRINOX, FOLFOXIRI, IROX, CHOP, R-CHOP, RCHOP-21, Mini-CHOP, Maxi-CHOP, VR-CAP, high-dose CHOP, EPOCH, dose-adjusted EPOCH, R-EPOCH, CODOX-M, IVAC, HyperCVAD, R-HyperCVAD, SC-EPOCH-RR, DHAP, ESHAP, GDP, ICE, MINE, CEPP, CDOP, GemOx, CEOP, CEPP, CHOEP, CHP, GCVP, DHAX, CALGB These include, but are not limited to, multidrug treatment regimens such as 8811, HIDAC, MOpAD, 7+3, 5+2, 7+4, MEC, CVP, RBAC500, DHA-Cis, DHA-Ca, DHA-Ox, RCVP, RCEPP, RCEOP, CMV, DDMVAC, GemFLP, ITP, VIDE, VDC, VAI, VDC-IE, MAP, PCV, FCR, FR, PCR, HDMP, OFAR, EMA / CO, EMA / EP, EP / EMA, TP / TE, BEP, TIP, VIP, TPEx, ABVD, BEACOPP, AVD, Mini-BEAM, IGEV, C-MOPP, GCD, GEMOX, CAV, DT-PACE, VTD-PACE, DCEP, ATG, VAC, VelP, OFF, GTX, CAV, AD, MAID, AIM, VAC-IE, ADOC, or PE.

[0085] Exemplary drugs that may be included in the drug delivery devices described herein include, but are not limited to, those used in chemotherapy, such as alkylating agents, plant alkaloids, antitumor antibiotics, antimetabolites, or topoisomerase inhibitors, enzymes, retinoids, or corticosteroids. Exemplary chemotherapy drugs include, by way of example only, 5-fluorouracil, cisplatin, carboplatin, oxaliplatin, doxorubicin, daunorubicin, idarubicin, epirubicin, paclitaxel, docetaxel, cyclophosphamide, ifosfamide, azacitidine, decitabine, bendamustine, bleomycin, bortezomib, busulfan, cabazitaxel, carmustine, cladribine, cytarabine, dacarbazine, etoposide, fludarabine, gemcitabine, irinotecan, leucovorin, melphalan, methotrexate, pemetrexed, mitomycin, mitoxantrone, temsirolimus, topotecan, valrubicin, vincristine, vinblastine, or vinorelbine.

[0086] Furthermore, all terms used in the claims should be interpreted according to their ordinary meaning in the art unless expressly defined otherwise herein. All references to "a / an / the element, device, component, means, etc." should be interpreted broadly as referring to at least one instance of the element, device, component, means, etc., unless expressly stated otherwise. [Brief explanation of the drawings]

[0087] Embodiments of the inventive concept will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0088] [Figure 1] 1 shows a perspective view of a medication delivery device having a drive unit according to the present invention; [Figure 2] 2 shows a schematic perspective view of the components of the drive unit of FIG. 1; [Figure 3]1 shows an example of measured back electromotive force values ​​of a rotating stepping motor. [Figure 4] 1 shows a flow chart of the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0089] 4 illustrates a method for detecting a stall state of a stepper motor during rotation. Preferably, the method is for detecting a stall state of a stepper motor during rotation of a medication delivery device. The method includes the steps of: first, measuring a back electromotive force (back EMF) value of the rotating stepper motor (401); second, calculating a fluctuation amplitude (a difference between a maximum back EMF value and a minimum back EMF value) (referred to herein as a "spread") of the back EMF value; in other words, calculating a first spread of the back EMF value (402); third, calculating a second spread of the back EMF value that occurs after the first spread (403); then, comparing the second spread with the first spread (404); and finally, determining that the stepper motor is stalled when the difference between the second spread and the first spread is greater than a first predetermined value (405). If the difference between the second spread and the first spread is not greater than the first predetermined value, the method resumes at step 402 of calculating the first spread of the back EMF values ​​again. Note that the first spread occurs before the second spread. The period between the first spread and the second spread is design dependent.

[0090] Because the back EMF value fluctuates (oscillates), the present method dynamically measures and compares the amplitude of the back EMF value fluctuations (referred to herein as "spread"). Instead of simply using a preset threshold, the back EMF value spread is analyzed and compared with previously collected data. Because the back EMF value oscillations appear differently with load changes as well as during stalls, as shown in Figure 3, stalls in a rotating stepper motor can be detected. Furthermore, back EMF oscillations are always present in a rotating motor, even under very light loads. Therefore, the stepper motor can maximize its available motor power rather than being stopped early by a safety margin typically set to prevent stalls. Furthermore, because the back EMF value fluctuations can be measured over a short period of time, stalls can be detected very early, before they cause damage to the motor.

[0091] Figure 3 shows an example of measuring the back EMF value vs. time T of a rotating stepper motor. Section A of the measured back EMF value is measured when the stepper motor starts to rotate and there is no load connected to the motor. Section B of the measured back EMF value is measured when the stepper motor is rotating and there is a 60 Newton (N) load connected. Section C of the measured back EMF value is measured when the stepper motor is rotating and the motor is stalled. Because the spread of the back EMF value when the motor is stalled is larger (compared to when the motor is not stalled), a motor stall can be detected by comparing the later spread (second spread) with the previously measured spread (first spread).

[0092] In a preferred example, the step of measuring the back electromotive force value of the rotating stepping motor further includes the steps of recording the back electromotive force value, and starting to calculate the first and second spreads only when the recorded back electromotive force value is lower than a second predetermined value E.

[0093] As can be seen from Figure 3, when a rotating stepper motor is connected to a load, a large spread occurs (section D in Figure 3). To prevent false detection, it is preferable to record the back EMF value and compare it with a second predetermined value before measuring the spread to confirm that the stepper motor is connected to a load (i.e., the motor is in use). As can be seen from Figure 3, the back EMF value is low when the motor is connected to a load. This allows the definition of the second predetermined value E. That is, by detecting the stall state of a rotating stepper motor based on the comparison result between the first spread and the second spread and the comparison result between the detected back EMF value and the second predetermined value, the accuracy of detecting the stall state of the rotating stepper motor can be improved.

[0094] Furthermore, in another preferred example, the second predetermined value is defined by the steps of acquiring the rotational speed of the stepping motor and determining the second predetermined value by searching for data from the first predetermined table using the acquired rotational speed of the stepping motor.

[0095] Since the back EMF value is also affected by multiple factors such as rotation speed and / or maximum spread level, the second predetermined value E can be dynamically defined by looking up a first predetermined table for a particular speed.

[0096] The rotational speed of the stepper motor can be obtained either by measuring the rotational speed or by receiving a signal containing the predetermined rotational speed of the stepper motor, for example, input by a user or by reading an RFID tag on the motor.

[0097] By measuring the back EMF value, several other measurements can be made. For example, the back EMF value of the stepper motor can be measured while the stepper motor is rotating, and the load value of the stepper motor can be determined by comparing the measured value with a third predetermined value. The third predetermined value can be determined by searching data from a second predetermined table using the acquired rotational speed of the stepper motor.

[0098] 1 and 2 show a medication delivery device including a drive unit 1. As shown in Fig. 2, the drive unit includes a stepper motor 13 and a processor electrically connected to the stepper motor 13, and is configured to execute the above-described method. In a preferred example, the drive unit 1 is reusable and configured to be releasably attached to a cassette 2. Preferably, the cassette 2 is disposable.

[0099] The housing 10 is configured to receive a portion of the cassette 2. In one example, the housing 10 includes a fastener 101 configured to releasably engage with a counter fastener 202 of the cassette 2. Preferably, the fastener 101 and the counter fastener 202 form a bayonet engagement, as shown in FIG.

[0100] In this example, the cassette 2 is partially received within the housing 10. Alternatively, the cassette may be fully received within the drive unit housing. In this example, no fixtures or counter-fixtures are required, as the cassette can be made with a shape that matches the receiving chamber of the drive unit housing.

[0101] The housing 10 includes an electronics unit 16. The electronics unit 16 includes a PCB 160 including a processor, e.g., an MCU or CPU, a battery 161, a switch 163, and optionally at least one of a second switch, a communication unit, a vibration motor, a buzzer, a camera, a microphone, and a sensor set. The communication unit can be based on a wired communication technology or a wireless communication technology, e.g., RFID, NFC, Bluetooth, Zigbee, LTE, 3G, 4G, 5G, etc. The communication unit can be configured to receive data / information (e.g., an RFID reader, an NFC reader, a Bluetooth receiver, a barcode reader, or an OCR reader) and / or to transmit signals (e.g., a Bluetooth beacon, an RFID / NFC transmitter). The sensor set includes at least one of a gyro sensor, an accelerometer, a temperature sensor, and a photo sensor.

[0102] The housing 10 includes an inner housing 102. The inner housing 102 includes an inner wall 1021.

[0103] The medication delivery device includes a plunger rod operably connected to a stepper motor 13, such that the plunger rod is moved by the stepper motor into the medication container to expel the medication contained therein. In a preferred example, the plunger rod is connected to the stepper motor via a lead screw. For example, the plunger rod is removably attached to the proximal end of the lead screw. The lead screw 11 extends along a longitudinal axis L between a proximal end and a distal end within the housing 10. In one example, the housing 10 extends along the longitudinal axis L between the proximal end and the distal end, as shown in FIGS. 1 and 2. Alternatively, the longitudinal axis of the lead screw is transverse to the axis along which the housing extends. The lead screw 11 includes a screw thread 110 extending between the proximal end and the distal end. The lead screw 11 includes a plunger rod 111 configured to move into the cassette 2 to expel the medication contained therein. In one example, the inner housing 102 includes a channel portion configured to guide the movement of the lead screw 11. Alternatively, the lead screw is a plunger rod.

[0104] The processor is configured to perform the above-described method, particularly for the purpose of detecting the state of the plunger rod, such as the position of the plunger rod and / or the speed of movement of the plunger rod. For example, the processor can determine the position of the plunger rod based on detecting the rotation of a stepper motor.

[0105] The processor is configured to pause, slow down, or resume rotation of the stepper motor when the processor determines that the stepper motor has stalled. Furthermore, since the processor is configured to detect the position of the plunger rod based on the rotation of the stepper motor, the processor is preferably programmed to calibrate the detection when a motor stall is detected. For example, by calculating the rotation angle based on a previously measured rotation angle and duration of the detected motor stall. Alternatively, or additionally, the driver unit includes an encoder and / or an optical sensor, e.g., an optical navigator such as a mouse sensor, electrically connected to the processor. In this example, the position of the plunger rod can be detected by the encoder and / or the optical sensor.

[0106] Further, in another example, the lead screw distal end 12 includes a surface 121a facing transversely to the longitudinal axis L. As the lead screw distal end 12 moves along the longitudinal axis L, the surface 121a abuts the inner wall 1021 of the housing 10. The lead screw distal end 12 includes a non-circular cross-section perpendicular to the longitudinal axis L, and the inner wall 1021 of the housing 10 includes a non-circular cross-section perpendicular to the longitudinal axis L, such that the lead screw distal end 12 is rotationally fixed to the housing 10. The lead screw distal end includes an outer surface having a non-circular cross-section perpendicular to the longitudinal axis L, and the inner wall of the housing includes an inner surface having a non-circular cross-section perpendicular to the longitudinal axis L. In one example, the entire outer surface of the lead screw distal end has a non-circular cross-section perpendicular to the longitudinal axis L, i.e., the non-circular cross-section is observable from the distal end of the lead screw distal end and from the proximal end of the lead screw distal end. Alternatively, a portion of the outer surface of the distal end of the lead screw has a non-circular cross-section perpendicular to the longitudinal axis L, i.e., the non-circular cross-section is only observable from either the distal end of the lead screw or the proximal end of the lead screw. Similarly, the inner wall of the housing may be arranged so that the entire inner surface of the inner wall has a non-circular cross-section perpendicular to the longitudinal axis L, or so that a portion of the entire inner surface of the inner wall has a non-circular cross-section perpendicular to the longitudinal axis L.

[0107] It is common to have small gaps between components during manufacturing to address tolerance issues, which means that the injection molding process may not create all identical components, so components that are designed to always touch each other in a product may result in significant waste for components that cannot fit together. Thus, the term "adjacent" means that two objects are "close" to each other, but do not necessarily touch each other.

[0108] In one example, the engagement formed between the distal end 12 of the lead screw and the inner wall 1021 of the housing 10 is a rib-rib engagement or a rib-groove engagement. In one example, the distal end 12 of the lead screw includes a groove 121 in the nut body 120, and the inner wall 1021 includes a rib 1021a positioned in the groove 121. The rib 1021a extends in the direction of the longitudinal axis L. When the distal end 12 of the lead screw is moved along the longitudinal axis L, the groove 121 moves along the rib 1021a. Alternatively, the distal end of the lead screw includes a polygonal cross-section perpendicular to the longitudinal axis L, and the inner wall of the housing includes a polygonal cross-section perpendicular to the longitudinal axis L. When the distal end of the lead screw is moved along the longitudinal axis L, the distal end of the lead screw moves along the inner wall. Therefore, rotation between the housing and the distal end of the lead screw can be prevented.

[0109] In a preferred example, the distal end of the lead screw can provide a function for determining the emitted dose. In one example, the inner wall includes a radial protrusion extending toward the longitudinal axis L. The radial protrusion is configured to block proximal movement of the distal end of the lead screw, thereby blocking proximal movement of the lead screw. Therefore, only a certain amount of the drug in the cassette of the medication delivery device can be released. In another example, the inner wall includes multiple radial protrusions axially and circumferentially offset from each other. In this example, different shapes of the distal end of the lead screw can be used to determine different deliverable doses. For example, the lead screw is formed by a main section and a distal section. The distal section is removably attached to the main section to form the lead screw. In one example, the distal section is replaceable. In one example, a set of distal sections of the lead screw can be provided. Each of the distal ends of the lead screw is formed to have a different cross-sectional shape when viewed along the longitudinal axis L. In this example, the distal end of the lead screw is defined by one of the different distal portions, which is configured to be blocked by at least one of the plurality of protrusions on the inner wall at a different axial location relative to the housing than the other distal portions. For example, one of the distal portions of the lead screw includes a triangular cross-section when viewed along the longitudinal axis L. Another of the distal portions of the lead screw includes a rectangular cross-section when viewed from the longitudinal axis L. In this example, at least one of the plurality of protrusions on the inner wall of the housing is configured to block the distal portion of the rectangular lead screw at one location, but at least one of the plurality of protrusions is configured to be spaced apart from the distal portion of the triangular lead screw. Thus, the distal end of the triangular lead screw can be blocked at another location proximal to the distal portion of the rectangular lead screw.

[0110] It should be noted that the use of the distal end of the lead screw to provide the functionality of determining the emitted dose is optional, since the drive unit 1 can control the deliverable dose by controlling the motor. In one example where the distal end of the lead screw provides the functionality of determining the dose, the housing can be generic, and different distal ends of the lead screw can be used to limit the travel distance of the lead screw. The hard stop of the lead screw can be used as a safety mechanism to limit the maximum deliverable dose of medication to the patient. This reduces the risk of overdosing if the electronics 16 is programmed with inaccurate medication information, e.g., due to misprogramming by a user, or if the cassette 2 contains an incorrect tag, e.g., due to an error on the manufacturing line.

[0111] The stepper motor 13 is rotatable around the lead screw 11 within the housing 10. The stepper motor 13 is engaged with the lead screw 11 via a threaded engagement. The stepper motor 13 is connected to the electronics 16 such that the electronics 16 controls the rotation of the stepper motor 13. As the stepper motor 13 rotates, torque is transmitted to the lead screw 11 via the threaded engagement between the lead screw 11 and the stepper motor 13. In one example, the drive 13 is connected to the electronics 16 via wires 131. Because the lead screw 11 is rotatably fixed to the housing 10, torque from the stepper motor 13 is converted into axial movement of the lead screw 11. In a preferred example, the stepper motor 13 is electrically connected to a switch 163. As shown in FIG. 5, the motor includes a rotor 130 and a channel 133 extending through the rotor 130. The lead screw 11 is partially positioned within the channel 133. In a preferred example, the longitudinal axis L is the central axis of the motor. In one example, the channel includes threads 134 extending around the channel. The threads engage with the threads of the lead screw. Alternatively, the drive unit includes a connector 135 operably connected to the rotor 130, such that the connector 135 is configured to be rotated by the rotor. In this example, the channel extends through the connector and is aligned with the channel of the rotor 130 along the longitudinal axis L. The channel of the connector 135 includes threads 134 extending around the channel of the connector 135. The threads 134 engage with the threads of the lead screw 11. In this example, the connector 135 is attached to the rotor 130. In a preferred example, the connector 135 and the rotor 130 are made of different materials. Because the threads 134 of the connector 135 are configured to engage with the lead screw 11, the connector 135 can be selected with a material that will produce low friction. In one example, the rotor 130 is made of metal, the lead screw 11 is made of metal, and the connector 135 is preferably made of plastic.

[0112] A switch 163 is disposed within the housing. The switch 163 is movable between an inactive position, in which both the processor and the stepper motor are deactivated, and an active position, in which the processor is activated. Optionally, the switch 163 is also configured to be used to turn on the stepper motor 13. Upon activation of the switch 163, rotation of the stepper motor 13 about the lead screw 11 is configured to move the lead screw 11 proximally, such that a stopper of a drug container M in the cassette 2 is moved by the lead screw 11.

[0113] The switch can be manually activated by a user of the medication delivery device. In one example, the switch is a button protruding from the outer surface of the housing. Alternatively, the housing includes a touch panel and the switch is an electronic switch that can be activated via the touch panel. Alternatively, the switch can be moved from an inactive position to an active position when the cassette 2 is attached to the housing of the drive unit 1.

[0114] In a preferred example, stepper motor 13 is configured to reciprocate the movement of lead screw 11. In one example where stepper motor 13 is a motor, the motor can be programmed to rotate in the opposite direction when an increase in resistance is detected (e.g., by detecting an increase in current). Alternatively, stepper motor 13 is designed to deliver only a preset dose, such that the motor rotates in the opposite direction once the preset dose has been delivered. Alternatively, stepper motor 13 is configured to rotate in the opposite direction when a switch is deactivated.

[0115] Thus, when switch 163 is activated, motor rotor 130 begins to rotate, thereby causing lead screw 11 to expel medication from cassette 2. When medication container M is empty, movement of lead screw 11 toward the outlet of medication container M is blocked by medication container M. Thus, an increase in resistance can be detected, and thus the motor can begin to rotate in the opposite direction. For example, if the motor is rotated clockwise about longitudinal axis L to expel medication, when an increase in resistance is detected, the motor can be rotated counterclockwise about longitudinal axis L. Thus, because lead screw 11 is rotatably fixed to housing 10, lead screw 11 moves distally.

[0116] In one example, the drive unit 1 includes a second switch housed within the housing 10. The second switch is aligned with the distal end 12 of the lead screw along the longitudinal axis L. The second switch is positioned distally away from the distal end 12 of the lead screw. The second switch is configured to be switched by the distal end 12 of the lead screw when the lead screw is moved distally relative to the stepper motor, such that the motor is stopped when the second switch is switched. Thus, at the end of the drug delivery operation, the lead screw 11 is moved distally relative to the housing 10 by the motor as described above, and the motor continues to rotate until the second switch is switched off by the distal end 12 of the lead screw. In a preferred example, when the second switch is switched by the distal end 12 of the lead screw, the second switch is configured to switch off the entire electronics unit 16. Alternatively, the second switch is configured to place the electronics unit 16 in a low-power mode.

[0117] In one example, the second switch is configured to be toggled by being pushed distally relative to the housing by the distal end of the lead screw. Furthermore, the second switch includes a flip arm. The second switch is configured to be toggled when the flip arm is pivoted by the distal end 12 of the lead screw, as shown in FIG. 8 . In this example, the second switch optionally includes a flexible member, such as a spring or flexible arm, configured to urge the second switch toward the distal end 12 of the lead screw, such that when the distal end 12 of the lead screw is moved away from the second switch, the second switch is moved to its original position. Alternatively, the second switch is a reed switch, and the distal end of the lead screw includes a magnet. Therefore, the distal end of the lead screw does not need to be in physical contact with the second switch to toggle it.

[0118] Furthermore, the drive unit 1 is provided with a communication unit, in one example, which is configured such that the communication unit is activated when the switch 163 is activated.

[0119] Another aspect of the present invention provides a medication delivery device comprising a drive unit 1 and a cassette 2. The cassette 2 comprises a body 20 having a counter-fixture 202 releasably attached to a fixation 101 of the housing 10 of the drive unit 1, and a delivery member cover 21.

[0120] The body 20 extends axially between a proximal end and a distal end. The delivery member cover 21 includes a proximal portion 210 and a distal portion 211.

[0121] The delivery member cover 21 is telescopic relative to the proximal end of the body 20 between an extended position in which the delivery member cover 21 projects in the axial direction L from the proximal end of the body 20, and a retracted position.

Claims

1. 1. A method for detecting a stall condition in a rotating stepper motor, comprising the steps of: measuring a back electromotive force value of the rotating stepping motor; calculating a first spread step of the back EMF values, the first spread step being defined by a difference between a maximum back EMF value and a minimum back EMF value in a first variation of the back EMF values ​​when the stepper motor is rotating; calculating a second spread of the back EMF values, the second spread being defined by a difference between a maximum back EMF value and a minimum back EMF value in a second variation of the back EMF values ​​when the stepper motor is rotating; comparing the second spread to the first spread; determining that the stepping motor is stalled when a difference between the second spread and the first spread is greater than a first predetermined value; A method comprising:

2. The step of measuring the back electromotive force value of the rotating stepping motor includes the steps of: recording the back EMF value; starting to calculate the first spread and the second spread only when the recorded back electromotive force value is lower than a second predetermined value; The method of claim 1 further comprising:

3. The second predetermined value is selected in the following order: acquiring a rotational speed of the stepping motor; determining the second predetermined value by searching data from a first predetermined table using the acquired rotational speed of the stepping motor; The method of claim 2 , defined by:

4. The step of obtaining the rotational speed of the stepping motor includes: The method of claim 3 including the step of measuring the rotational speed of the stepper motor.

5. The step of obtaining the rotational speed of the stepping motor includes:

4. The method of claim 3, further comprising receiving a signal comprising a predetermined rotational speed of the stepper motor.

6. The method comprises the steps of: measuring the back electromotive force value of the rotating stepping motor; comparing the measured value to a third predetermined value; determining a load value of the stepper motor; The steps in said sequence may be carried out before or after any of the steps according to any one of claims 1 to 5. The method according to any one of claims 1 to 5.

7. Before the step of determining the value of the load on the stepper motor, the method further comprises: obtaining the rotational speed of the stepping motor; determining the third predetermined value by searching data from a second predetermined table using the acquired rotational speed of the stepping motor; The method of claim 6, comprising:

8. A processor of a drive unit of a medication delivery device, the drive unit comprising a stepper motor, the processor configured to perform the method of any one of claims 1 to 7.

9. 9. A drive unit for a medication delivery device, comprising: a stepper motor; a plunger rod operably connected to the stepper motor; and the processor of claim 8, wherein the processor is electrically connected to the stepper motor, and the plunger rod is configured to be driven by the stepper motor when the stepper motor rotates.

10. 10. The drive unit of claim 9, wherein the processor is configured to stop, slow down, or resume the rotation of the stepper motor when the processor determines that the stepper motor is stalled.

11. 11. A drive unit according to claim 9 or 10, wherein the processor is configured to determine a position of the plunger rod based on detecting the rotation of the stepper motor.

12. 12. The drive unit of claim 9, wherein the drive unit comprises a housing configured to receive a cassette of a medication delivery device, the cassette being releasably attached to the housing, and the plunger rod being configured to move into a medication container in the cassette.

13. A drive unit according to any one of claims 9 to 12, wherein the drive unit comprises a switch movable between an inactive position in which the processor and the motor are both deactivated, and an active position in which the processor is activated.

14. 14. A drive unit as claimed in combination of claim 12 and claim 13, wherein the switch is configured to move from the inactive position to the active position when the cassette is attached to the housing.

15. A drug delivery device comprising a drive unit according to any one of claims 9 to 14, the drug delivery device being an injection device.

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