SYSTEM FOR CONTROLLING AN ELECTRIC MOTOR OF A PEDAL- ASSISTED BICYCLE

The present invention relates to a pedal-assisted light land vehicle. In particular, the present invention concerns the field of sustainable mobility and relates to a pedal-assisted bicycle or “e-bike”.

It should be specified that, in this context, a pedal-assisted bicycle is intended as any vehicle with one (unicycle), two, three (tricycle) or more wheels (quadricycle, rickshaw, etc.) an e-cargoBike (unicycle, tricycle or quadricycle) which is both driven by human muscle force, and is provided with at least one electric auxiliary motor.

As is known, a pedal-assisted bicycle or “e-bike” is a conventional bicycle to which at least one electric motor coupled to various types of reducers, one or more batteries and a series of sensors are applied which detect, instant by instant, the rotation speed of the pedal cranks-pedals assembly. The rotation speed detected is coded by a processing unit which, based on predefined parameters, calibrates the additional support provided by the electric motor to the muscle action provided by the cyclist.

To date, pedal-assisted bicycles use brushless or DC electric motors with permanent magnets or coupled to various types of reducers, which drive the shaft on which the cranks/pedals assembly, rotates, usually coaxial to the cranks.

In the state of the art, bicycles exist which are provided with an electric motor with the purpose of helping the user while pedalling.

Generally, such pedal-assisted bicycle technology comprises an electric motor, a rechargeable battery and an electronic management system (processing unit), by means of which the auxiliary torque input provided by the electric motor is managed. Thereby, the latter provides an auxiliary torque to the cyclist during pedalling in order to lighten the physical effort.

According to the prior art, bicycles exist which are provided with a more advanced electronic management system comprising an apparatus for detecting the torque exerted by the user on the pedal shaft in a bicycle transmission.

Measuring and monitoring the value of the torque generated on the pedal shaft generally allows to optimise the intervention of the electric motor during pedalling. In fact, the electronic management system provided on the electric bicycles processes the information received from the apparatus which detects the torque generated on the pedal shaft and activates/deactivates or partialises the work of the electric motor according to the needs.

Therefore, while pedalling, the cyclist will benefit from the intervention of the electric motor which will in part replace the user, reducing their physical effort; as soon as the pedalling load is reduced, the apparatus which detects the new motor torque value sends the information to the management system which will also make the torque dispensed by the electric motor decrease. Simultaneously with the intervention of the electric motor on the bicycle transmission, the user must take charge of managing the transmission ratio active on the transmission itself.

According to the prior art, the apparatus that measures the motor torque value comprises a motor torque sensor. In systems of the known type, depending on the thrust that the cyclist will exert on the cranks, the control unit through the feedback of the pedalling torque detector, will manage the delivery of the torque of the electric motor adapted to define the pedalling auxiliary motor force.

In other words, the current solutions for the realization of the pedal- assisted bicycles are mainly based on the use of a torque transducer placed on the axis of the cranks in order to detect the pressure and/or effort that the cyclist imparts. Consequently, the detected signal is managed by the control unit to increase and/or decrease the power delivered by the motor. Similarly, in generic applications of known type, the maximum power deliverable by the motor is defined by a further parameter that can be called the assistance level (1 , 2, 3...). The assistance level is usually set manually by the biker through the usual HMI interfaces that the motor manufacturer makes available.

The assistance levels can be changed (manually) during the travel in such a way as to increase the maximum deliverable power of the electric motor. Therefore, in systems of known type, the variation of the assistance level is at the discretion of the biker. A disadvantage of the prior art is that the delivery of the auxiliary torque by the electric motor does not take place in a controlled manner based on the real needs of auxiliary torque.

Another disadvantage of the prior art is that the delivery of auxiliary torque is usually controlled/delivered by dosing the amount of current delivered from the battery to the electric motor.

Another disadvantage of the prior art is that the user has to manually act on the mechanical gearbox of the land vehicle.

A further disadvantage of the known constant current electric motors is that in order for the motor to deliver a high torque at low speed, the torque coefficient must be increased by increasing the number of revolutions of each phase.

In this context, the technical task underlying the present invention is to propose a pedal-assisted light land vehicle that overcomes the drawbacks of the above-mentioned prior art.

An object of the present invention is to propose a pedal-assisted light land vehicle that takes into account not only the pedalling torque, but also other parameters such as the travel, the fatigue state of the cyclist and the residual charge of the battery.

A further object of the present invention is to propose a pedal-assisted light land vehicle that is capable of providing optimal pedal-assistance in terms of performance and energy efficiency.

Another object of the present invention is to make available a system for the precise management of the auxiliary torque delivered by the electric motor. A further object of the present invention is to make available a pedal- assisted land vehicle that allows an increase in performance in the presence of high loads (eCargobike) and/or changes in slope of the route.

A further object of the present invention is to allow an automatic management of the auxiliary torque delivered without the need for interventions by the cyclist in the definition of the motor assistance parameters.

The invention therefore aims to objectify the assistance (modulation of the maximum deliverable power of the motor) as a function of state parameters described as: biometric, biker’s travel and battery charge state, transport load sensors.

Another object of the present invention is to make available a pedal- assisted land vehicle that is simple to use and reliable.

A further object of the present invention is to realize a pedal-assisted land vehicle having affordable costs.

The specified technical task and the specified purposes are substantially achieved by a pedal-assisted light land vehicle comprising the technical features set forth in one or more of the appended claims.

SUMMARY OF THE INVENTION

The present invention describes a pedal-assisted light land vehicle as described in appended claim 1 .

Other advantageous aspects of the reducer assembly are described in dependent claims 2 to 14.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to appreciate the advantages thereof, some non-limiting example embodiments thereof are described herein below, referring to the appended drawings, in which:

- figure 1 schematically illustrates a pedal-assisted bicycle according to the present invention;

- figure 2 illustrates a gearmotor assembly of the pedal-assisted bicycle of figure 1 ; - figure 3 illustrates an exploded detail of figure 2;

- figure 4 schematically illustrates a functional block diagram of the processing unit and of the sensors according to an embodiment of the present invention.

DETAILED DESCRIPTION

With reference to the attached figures, a pedal-assisted land vehicle, in particular, represented as an e-bike, has been indicated overall with reference number 10.

The bicycle 10 comprises two wheels 12, a frame with a housing for a battery 16, a pedals/cranks assembly 13, a transmission 14 configured for the transmission of the motion from the shaft of the cranks 13 to the drive wheel 12 and an electric motor 21 .

The electric motor 21 is configured to function both as a motor and as a generator associated with a wheel 12 of the light land vehicle 10 and comprises a rotation shaft 22, a stator and a rotor having one or more phases with relative windings or turns. Preferably, the electric motor 21 is three-phase.

The bicycle 10 may comprise a gearmotor 20.

The pedals/cranks assembly 13, for pedalling by an operator of the light land vehicle, comprises a rotation axis 26.

A detail of the gearmotor 20 is illustrated in exploded form in Figure 3.

In particular, the gearmotor 20 comprises the electric motor 21 , configured to function both as a motor and as a generator associated with a wheel 12 of the light land vehicle 10 and comprising a rotation shaft 22, a stator and a rotor having one or more phases with relative windings or turns.

The gearmotor 20 is powered by a rechargeable battery 16 placed in an energy exchange relationship with said electric motor 21 , a reducer assembly 25 operatively interposed between the rotation shaft 22 of the electric motor 21 and the rotation axis 26 of the pedalling assembly 13. In a preferred, but non-limiting embodiment of the present invention, the land vehicle 10 comprises an electric motor 21 positioned on the hub of the rear wheel.

Finally, a transmission 14 operatively interposed between the pedalling assembly 13 and the wheel 12 of the light land vehicle and a torque sensor 40 configured to detect a thrust torque at said pedalling assembly 13 and to generate a respective signal S1 representative of said pedalling torque are part of the land vehicle 10. Preferably, the torque sensor is arranged in the vicinity of the cranks.

Advantageously, the land vehicle also comprises a second sensor configured to detect a state parameter and to generate a respective signal S2, S3, S4, Si representative of said state parameter detected by the second sensor. In this case, the driving module 32 is configured to provide the electric motor 21 with a command signal as a function of said signal representative of the pedalling torque S1 and as a function of said state parameter detected by the second sensor.

There are also one or more biometric sensors 41 configured to detect one or more biometric parameters of the operator of the land vehicle and to generate one or more respective signals S2, S3, S4 representative of said biometric parameters, a sensor 42 configured to detect the charge state of the battery 16 and to generate a respective signal S5 representative of the charge state of the battery 16, a sensor 43 configured to detect one or more parameters representative of the travel state of the land vehicle and to generate one or more respective signals S6, S7, S8 representative of the travel state of the land vehicle. The land vehicle may then comprise a plurality of sensors configured to detect a plurality of state parameters S1 , S2, S3, S4, S5. In such a case, the driving module 32 is configured to provide the electric motor 21 with a command signal as a function of said signals representative of the state parameters. The set of the signals defined as state parameters (S1 , S2,....) are configured to condition the pedalling assistance level. The bicycle 10 comprises a control unit 30 associated with one or more of said sensors 40, 41 , 42, 43 and said electric motor 21 and comprising a control/driving module 32 configured to provide the electric motor 21 with a command/electric power signal as a function of said signals representative of the pedalling torque, biometric parameters, charge state of the battery and travel state of the land vehicle. In other words, the processing unit 30 processes the operating conditions of the entire system considering the actual conditions of travel, fatigue of the cyclist and residual charge of the battery 16. Consequently, as a function of these input state parameters/signals, the unit 30 processes the optimal assistance strategy in terms of performance and energy efficiency. In general, it should be noted that in the present context and in the subsequent claims, the control unit 30 is presented as subdivided into distinct functional modules (memory modules or operating modules) for the sole purpose of describing the functionalities thereof clearly and completely.

In reality, the control unit 30 can consist of a single electronic device, suitably programmed to perform the functions described, and the various modules can correspond to hardware entities and/or routine software belonging to the programmed device.

Alternatively, or additionally, such functions can be performed by a plurality of electronic devices over which the aforesaid functional modules can be distributed.

The control unit 30 can also rely on one or more processors to execute the instructions contained in the memory modules.

Moreover, the aforesaid functional modules can be distributed over different local or remote computers based on the architecture of the network in which they reside.

The systems further comprise all means and/or memory and/or operating modules necessary to implement the functions described in the respective described methods.

The present invention advantageously provides for an electronic control of the rotation speed of the drive shaft 22 of the electric motor. The variation of the speed of the drive shaft 22 is managed by a control and driving module 32 of the processing unit 30 configured to act on the number of turns of each phase winding of the electric motor 21 .

In particular, the winding of each phase is subdivided into two or more parts N1 , N2, Ni, each of which is connected to the driving module 32 of the electric motor 21 .

This subdivision of the windings of each phase takes place by means of a switching system for switching and combining the phase windings of the motor in order to change the resultant of the number of phase turns of the same.

Each part of the subdivision will contain a number of partial turns N1 , N2, .., Ni. This subdivision into several parts of each phase, allows to perform a combination such as to change the number of turns for each single phase and change the ratio between the electric driving force (fem) and the speed of rotation of the drive shaft 22.

The driving module 32 is able to change and switch the number of turns of the electric winding of each phase of the electric motor 21 by using an electromechanical and/or electronic switching system.

The driving module 32 is able to change and switch the number of turns of the electric winding of each phase of the electric motor 21 by using MOSFET and/or IGBT (electronic switch).

The driving module 32 is configured to connect in series the partial windings N1 , N2,..., Ni of each phase, when there is a need to increase the useful pedalling assistance torque and to increase the voltage constant, and to connect in parallel the partial windings N1 , N2,..., Ni of each phase, when there is a need to decrease the torque constant and the voltage constant.

Furthermore, the driving module 32 is further configured to connect said one or more phases of the electric star or triangle motor 21 , in case of excessive decay of the residual voltage of the battery 16 during the travel of the bicycle 10.

In other words, the driving module 32 is configured to vary the ratio between nominal speed and maximum voltage available to the battery 16 in the following ways:

1) Serial and parallel management of the number of turns of the winding of each single phase;

2) Management of the connection of the triangle or star motor phases. In both cases use is made of the entire winding of each phase.

The electric motor 21 is a synchronous electric motor with permanent magnets or a magnetic reluctance electric motor or an asynchronous motor. In both cases, the winding of each phase is subdivided into two or more parts, so as to perform a combination such as to be able to change the number of turns for each single phase and to change the ratio between the fem (electromotive force) and the rotation speed of the drive shaft 22. Advantageously, the driving module 32 acts directly on the electric motor 21 by means of a speed vector type control through the feedback of a mechanical sensor of relative position of the rotor with respect to the stator of the electric motor 21. In other words, the vector control takes place through the feedback of a position sensor (encoder/resolver or equivalent) that instantly identifies the relative position of the rotor.

The driving module 32 of the electric motor acts on the electric motor 21 by means of a flow observer configured to estimate the actual relative position of the rotor with respect to the stator by means of a closed loop estimation scheme (sensorless).

Such an implementation allows a greater robustness, since it is an estimator of a measured quantity of some electrical quantities, so that from the comparison between the measurement of such electrical quantities and the estimate an error signal is obtained that further corrects the estimate. In this way, by using the sensorless technology, an estimate can be made without the use of a physical encoder.

The biometric parameters of the operator of the land vehicle comprise one or more of at least instantaneous heartbeat, average heartbeat, blood oxygen saturation level.

The land vehicle may comprise a load sensor configured to detect additional loads (in addition to the weight of the cyclist) positioned on the land vehicle and to generate a respective signal S9 representative of the additional load positioned on the land vehicle.

The parameters representative of the travel state of the land vehicle comprise one or more of at least the total distance to be travelled, the average height differences of the planned route, the altitude of the planned route and/or the external temperature.

The control unit 30 comprises a wireless communication module capable of interfacing with said sensors and with one or more external personal electronic devices and configured to receive said parameters detected by said sensors; and/or to receive and/or transmit data from/to one or more external electronic devices.

The wireless communication module and the various sensors interface with the processing unit 30 so as to transfer the various control parameters in real time.

Advantageously, the parameters representative of the travel state of the land vehicle 10 are detected by one or more external personal electronic devices 35 and sent in wireless connection to said wireless communication module of said control unit 30.

Figure 4 schematically illustrates a personal electronic device 35 connected to the processing unit 30 via a telecommunication or telematic network.

Preferably, the mobile electronic device 35 is one among at least one smartphone, tablet or a portable computer.

The telematic network 30 is preferably the Internet network, but also an intranet network or any private network adapted to implement a clientserver type or cloud type or mixed type communication protocol. The telematic network is connected, where necessary, to mobile communication networks.

The main electronic device 35 may function by means of a telephone operator sim and/or wi-fi and/or Bluetooth.

The control unit 30 comprises a display module 33 connected to an external control panel configured to display the parameters detected by the various sensors, e.g., battery state, travel speed, etc.

The control panel also allows to make selections of the driving modes of the land vehicle through a special interface element (keyboard or touch screen). The control panel is also configured for the entry and/or the acquisition from personal mobile devices 35 of general data of the cyclist (input), such as by way of non-limiting example, weight, height, bpm max and training level (0,1 ,2).

Advantageously, the display and/or the control panel can be constituted by the personal electronic device 35 of the cyclist, by means of the connection with the communication module 33 and with the user interface or display module 34.

Light land vehicle means a mountain bike (for those using the bike in the mountains, on dirt, muddy, bumpy and uphill terrain), a racing bike (for those using the bike on asphalt, for long pedalling, and looking for a light and snappy vehicle), a city bike (for those moving mainly within the urban context), a trekking bike (a mix between city bikes and MTBs), a folding bike (for those having to transport the bike by train or on other means of transport) and/or an e-cargo bike (for those needing more space to carry loads or to transport their children to school).

Example of e-bike operation

In the specific case, by way of non-limiting example, a 250W electric motor whose winding of each single phase is divided into two parts is considered. N1 and N2 are defined as the number of partial turns, respectively, of each single division. Each single division of the motor phase winding is connected to the switching system (driving module 32).

The system of the electronic speed gearbox of the drive shaft 22 (switching system) is based on the principle of defining the nominal speed of the motor 21 based on the number of turns of the winding and the maximum voltage available. In the event that there is no need to increase the torque constant of the motor (Nm/A) in order to increase the auxiliary torque useful for assistance and also to increase the voltage constant (Volt/rpm), the partial windings will be connected in series (Ntot = N1 +N2). Otherwise, where it will be necessary to decrease the torque constant and the voltage constant, the connection of the windings of the motor 21 will be in parallel.

The control and driving strategy is based on the analysis of the input variables described above. For example, in the event that the route presents a positive slope and/or a fatigue of the cyclist is detected (bpm > "training level” x "bpm max”), the driving module 32 will tend to increase the pedalling assistance level, both as a function of the load levels, the cadence (ppm) and the charge state of the battery and will act on the electric motor 21 so as to make pedalling assistance as efficient as possible.

A further intervention of the driving module is the connection of the star or triangle motor phases: in case of excessive decay of the residual voltage of the battery during the travel, the motor phases are connected as a triangle.

In the event that an established route is programmed, for example by entering it on one’s smartphone, the processing unit 30 will take into account the energy consumption necessary for the completion of the route (for example taking into account the type of route), by intervening, through the driving module 32, on the assistance level (i.e. auxiliary torque delivery) and on the intervention on the electric motor 21 . In this case, the control of the charge level of the battery becomes strategic to balance the assistance and allow the set route to be completed.

The present invention provides the following additional advantages: Optimization of the autonomy of the battery charge 16 and an increase in the performance of the pedal assistance.

In addition, given the presence of an optimized management of the nominal motor speed, it is possible to eliminate or minimize the use of the mechanical gearbox 14 for both e-bike and e-cargoBike applications.

The use of the electronic driving module 32 will avoid the use of motor defluxation (i.e. reduction of magnetic flux) to achieve the desired speed regime, increasing the efficiency of the entire system.

Monitoring the cyclist's bpm and the relative assistance management reduces fatigue in favour of the cyclist's well-being.

Preventive management of the charge state of the battery for the completion of the route also as a function of the load transported: added value especially in case of use of the e-cargoBike, where the completion of all deliveries is a strategic value.

It is clear that the specific features are described in relation to different embodiments of the invention by way of non-limiting example. The person skilled in the art will obviously be able to introduce further modifications and variants of the present invention with the aim of satisfying specific contingent needs. For example, the technical features described in relation to one embodiment of the invention can be extrapolated therefrom and applied to other embodiments of the invention. Such modifications and variations are moreover contained within the scope of the invention as defined by the following claims.