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Title:
MID-DRIVE UNIT FOR ELECTRIC BICYCLE
Document Type and Number:
WIPO Patent Application WO/2019/102495
Kind Code:
A1
Abstract:
A torque maintenance device that is adapted to a mid-drive unit has a sensor unit and a control unit to control the operations of an electric bicycle. The sensor unit includes a tilt sensor (130), a current sensor, a first cadence sensor (122) and a rotary cadence sensor (124). The control unit receives an assist level selected by a rider and sensed data from the sensor unit and determines a pedal torque based on a measured slope value, a current supplied to the motor (116), a weight of the rider and a speed of a pedal (126) and motor (116) sensed by the sensor unit. The control unit determines a motor torque to be provided to the electric bicycle based on the assist level, the slope value, the current, the pedal torque and weight of the rider for maintaining a torque of the electric bicycle as constant.

Inventors:
DHURI, Krishna Rao (356 G-Block, Sonesta Meadows Thubarahalli Extension Road, Thubarahalli, Bangalore 6, 560066, IN)
P, Parthiban (Farm House Kanchalli , Post - Basappanadoddi, Tehsil - Kollegal, Chamarajanagar 9, 571439, IN)
S.A, Anish (4th cross Bejai New Road, Mangalore 4, 575004, IN)
SATHUJODA, Prabhakar (Apartment 1, 114 Boundary Lane, Manchester Greater Manchester M15 6FD, M15 6FD, GB)
Application Number:
IN2018/050779
Publication Date:
May 31, 2019
Filing Date:
November 23, 2018
Export Citation:
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Assignee:
IVROOM POWER PRIVATE LIMITED (#356, G-block Sonesta Meadows, Thubarahalli Extension Road, Thubarahalli, Bangalore 6, 560066, IN)
International Classes:
B62M6/50
Foreign References:
EP2860096A12015-04-15
JP2005132274A2005-05-26
US20160159434A12016-06-09
Attorney, Agent or Firm:
BALA, Arjun Karthik (Global Incubation Services, CA Site NO 1 JSS Institutions Campus,,HAL 3rd stage, Behind Hotel Leela Palac, Kodihally Bangalore 8, 560008, IN)
Download PDF:
Claims:
CLAIMS

I/We claim:

1. A torque maintenance device that is adapted to a mid-drive unit of an electric bicycle, wherein torque maintenance device comprises:

a sensor unit that monitors an operation of an electric bicycle, wherein the sensor unit comprises

a tilt sensor (130) that senses data associated with a road surface at which the electric bicycle is running to measure a slope value of the road surface;

a current sensor that measures a current that is supplied to an electric motor

(116);

a first cadence sensor (122) that is positioned on a shaft (112) of a pedal to measure a speed of the pedal (126); and

a rotary encoder sensor (124) that is mounted on a co-axial shaft to the motor shaft (114), wherein the co-axial shaft and the motor shaft (114) are coupled by a second clutch (120) to measure a speed of the electric motor (116); and

a control unit that controls the mid-drive unit, wherein the control unit receives (a) an assist level selected by a rider using a control knob of the electric bicycle, and (b) sensed data from the sensor unit, wherein the control unit, characterized in that, comprises

a rider mass estimator module (402) that determines a weight of the rider, wherein the rider mass estimator module (402) employs a filtering technique to determine the weight of the rider based on the measured slope value of the road surface, the current that is supplied to the electric motor (116), the speed of the pedal (126), and the speed of the electric motor (116);

a pedal torque estimator module (404) that determines a pedal torque based on the measured slope value of the road surface, the current that is supplied to the electric motor (116), the speed of the pedal (126), the speed of the electric motor (116), and the weight of the rider; and

a motor torque determination module that determines a motor torque to be provided to the electric bicycle based on the assist level selected by the rider, the measured slope value of the road surface, the current that is supplied to the electric motor, the pedal torque and the weight of the rider for maintaining a torque of the electric bicycle as constant and for improving performance of the electric bicycle.

2. The torque maintenance device as claimed in claim 1, wherein the mid-drive unit comprise a gear unit, wherein the gear unit comprises a first gear (104), a second gear (106), a third gear (108) and a fourth gear (110), wherein the first gear (104) is mounted on the motor shaft (114), and the fourth gear (110) is mounted on a sleeve (133) that is coupled with the shaft (112) of the pedal (126) using a first clutch (118), wherein the control unit controls the electric motor to provide the determined motor torque to maintain the torque of the electric bicycle as constant.

3. The torque maintenance device as claimed in claim 2, wherein the mid-drive unit comprise a clutch unit comprising

(a) the first clutch (118) that is positioned between the shaft (112) of the pedal (126) and the sleeve (133) on which the fourth gear (110) is mounted, which allows the pedal torque coming in at independent speed; and

(b) the second clutch (120) that is positioned between the motor shaft (114) and the co-axial shaft, wherein the second clutch (120) enables coupling or decoupling of the electric motor (116) for running the electric bicycle by electric motor (116).

4. The torque maintenance device as claimed in claim 1, wherein the control unit comprises an Integrated Circuit (IC) board (132) for controlling the mid-drive unit, wherein the IC board (132) is positioned away from the electric motor (116) to avoid electromagnetic interference.

5. The torque maintenance device as claimed in claim 1, wherein the rider mass estimator module (402) is communicatively connected to at least one of the tilt sensor (130), the current sensor, the first cadence sensor (l22)or the rotary encoder sensor (124) to receive the sensed data, and wherein the pedal torque estimator module (404) is communicatively connected to at least one of the tilt sensor (130), the current sensor, the first cadence sensor (122), the rotary encoder sensor (124) or the rider mass estimator module (402) to receive the sensed or the estimated data.

6. The torque maintenance device as claimed in claim 1, wherein the sensed data obtained from the tilt sensor (130) are filtered to remove vibrations before estimating the weight of the rider and the pedal torque.

7. The torque maintenance device as claimed in claim 1, wherein the control knob and the mid-drive unit is connected using a wireless or a wired communication.

8. The torque maintenance device as claimed in claim 2, wherein the mid-drive unit comprises at least one structural plate (102A-N) to support the motor shaft, the shaft (112) of the pedal (126) or the gear unit to improve the strength, assembling and servicing of the electric bicycle, wherein the least one structural plate (102A-N) and the gear unit is made up of a composite material or any suitable material.

9. The torque maintenance device as claimed in claim 1, wherein the torque maintenance device comprises a cooling unit, wherein the cooling unit comprises:

a temperature sensor that is mounted inside the mid-drive unit, wherein the temperature sensor senses a temperature of the electric motor (116) when in operation and communicates the sensed temperature to the control unit; and

a cooling fan (128) that is activated by the control unit when the sensed temperature of the electric motor (116) exceeds a threshold level, for cooling the electric motor (116).

10. The method of maintaining a torque of an electric bicycle using a torque maintenance device, the method comprises:

monitoring, using a sensor unit, an operation of an electric bicycle, wherein the monitoring comprises:

measuring, using a tilt sensor (130), data associated a road surface at which the electric bicycle is running to measure a slope value of the road surface;

measuring, using a current sensor, a current that is supplied to an electric motor (116);

measuring, using a first cadence sensor (122), a speed of a pedal (126); and measuring, using a rotary encoder sensor (124), a speed of the electric motor (116), wherein the rotary encoder sensor (124) is mounted on a co-axial shaft to the motor shaft (114), wherein the co-axial shaft and the motor shaft (114) are coupled by a second clutch (120); and receiving (a) an assist level selected by a rider using a control knob of the electric bicycle, and (b) the sensed data from the sensor unit;

characterized in that,

determining, by employing a filtering technique, a weight of the rider based on the measured slope value of the road surface, the current that is supplied to the electric motor (116), the speed of the pedal (126), and the speed of the electric motor (116);

determining a pedal torque based on the measured slope value of the road surface, the current that is supplied to the electric motor (116), the speed of the pedal (126), the speed of the electric motor (116), and the weight of the rider; and

determining a motor torque to be provided to the electric bicycle based on the assist level selected by the rider, the measured slope value of the road surface, the current that is supplied to the electric motor (116), the pedal torque and the weight of the rider for maintaining a torque of the electric bicycle as constant and for improving performance of the electric bicycle.

Description:
MID-DRIVE UNIT FOR ELECTRIC BICYCLE

BACKGROUND

Technical Field

[0001] The embodiments herein generally relate to electric bicycles, and, more particularly, an electric bicycle that comprises a mid-drive unit with specific mechanical design and specific electronic device for high performance and cost-effective.

Description of the Related Art

[0002] Generally, bicycles are the cheapest means of transport for short distance. In terrain surfaces and upward slope surfaces, bicycles require more manual power from riders. Considerable efforts have been made in these previous years to overcome this problem by inventing electric bicycles.

[0003] The existing pedal assisted electric bicycles are normally just like ordinary bicycles but assisted with an electric motor to minimize manual power. Generally, motors are placed at the hub of the wheels. There are other types of bicycles, where motors are placed in mid of the frame. The drive system is called as a mid-drive unit (MDU). In a few cases, for improving the rider feel, a torque sensor is fitted inside the MDU. But the cost of the torque sensor is approximately 15-20%. The existing pedal assisted electric bicycles do not have an estimation mechanism to monitor or sense manual power from the rider. The above problem increases the price of the bicycle.

[0004] The existing pedal assisted electric bicycles further do not support monitoring the slope of the surface traveling and consume more manual power from the rider in upward slope areas. Generally, in upward slope times, more help should be sought from the motor; but unfortunately, it doesn’t happen. The above-mentioned problem does not give a good feel to the rider with existing pedal assisted electric bicycle. [0005] Accordingly, there remains a need for an electric bicycle with a cost-effective and high performance mid-drive unit design for electric bicycles.

SUMMARY

[0006] In view of the foregoing, an embodiment herein provides a torque maintenance device that is adapted to a mid-drive unit of an electric bicycle. The torque maintenance device includes a sensor unit and a control unit. The sensor unit monitors the operation of an electric bicycle. The sensor unit includes a tilt sensor, a current sensor, a first cadence sensor and a rotary encoder sensor. The tilt sensor senses data associated with a road surface at which the electric bicycle is running to measure a slope value of the road surface. The current sensor measures a current that is supplied to an electric motor. The first cadence sensor is positioned on a shaft of a pedal to measure a speed of the pedal. The rotary encoder sensor is mounted on a co-axial shaft to the motor shaft. The co-axial shaft and the motor shaft are coupled by a second clutch to measure a speed of the electric motor. The control unit controls the mid-drive unit which receives (a) an assist level selected by a rider using a control knob of the electric bicycle, and (b) sensed data from the sensor unit. The control unit, characterized in that, includes a rider mass estimator module, a pedal torque estimator module and a motor torque determination module. The rider mass estimator module determines a weight of the rider by employing a filtering technique based on the measured slope value of the road surface, the current that is supplied to the electric motor, the speed of the pedal, and the speed of the electric motor. The pedal torque estimator module determines a pedal torque based on the measured slope value of the road surface, the current that is supplied to the electric motor, the speed of the pedal, the speed of the electric motor, and the weight of the rider. The motor torque determination module determines a motor torque to be provided to the electric bicycle based on the assist level selected by the rider, the measured slope value of the road surface, the current that is supplied to the electric motor, the pedal torque and the weight of the rider for maintaining a torque of the electric bicycle as constant and for improving performance of the electric bicycle.

[0007] In some embodiment, the mid-drive unit includes a gear unit. The gear unit includes a first gear, a second gear, a third gear and a fourth gear. The first gear is mounted on the motor shaft and the fourth gear is mounted on a sleeve that is coupled with the shaft of the pedal using a first clutch. The control unit controls the electric motor to provide the determined motor torque to maintain the torque of the electric bicycle as constant.

[0008] In some embodiment, the mid-drive unit includes a clutch unit including the first clutch and the second clutch. The first clutch is positioned between the shaft of the pedal and the sleeve on which the fourth gear is mounted, which allows the pedal torque coming in at independent speed, and the second clutch is positioned between the motor shaft and a co axial shaft of the electric bicycle. The second clutch enables coupling or decoupling of the electric motor for running the electric bicycle by electric motor.

[0009] In some embodiment, the control unit includes an Integrated Circuit (IC) board for controlling the mid-drive unit. The IC board is positioned away from the electric motor to avoid electromagnetic interference.

[0010] In some embodiment, the rider mass estimator module is communicatively connected to at least one of the tilt sensor, the current sensor, the first cadence sensor or the rotary encoder sensor to receive the sensed data. The pedal torque estimator module is communicatively connected to at least one of the tilt sensor, the current sensor, the first cadence sensor, the rotary encoder sensor or the rider mass estimator module to receive the sensed or the estimated data.

[0011] In some embodiment, the sensed data obtained from the tilt sensor are filtered to remove vibrations before estimating the weight of the rider and the pedal torque.

[0012] In some embodiment, the control knob and the mid-drive unit is connected using a wireless or a wired communication.

[0013] In some embodiment, the mid-drive unit includes at least one structural plate to support the motor shaft, the shaft of the pedal or the gear unit to improve the strength, assembling and servicing of the electric bicycle, wherein the structural plate and the gear unit is made up of a composite material or a steel or an aluminum.

[0014] In some embodiment, the torque maintenance device includes a cooling unit. The cooling unit includes a temperature sensor and a cooling fan. The temperature sensor is mounted inside the mid-drive unit and senses a temperature of the electric motor when in operation and communicates the sensed temperature to the control unit. The cooling fan is activated by the control unit when the sensed temperature of the electric motor exceeds a threshold level, for cooling the electric motor.

[0015] In an aspect, a method for maintaining a torque of an electric bicycle using a torque maintenance device is provided. The method includes the following steps of (a) monitoring, using a sensor unit, an operation of an electric bicycle, wherein the monitoring includes the steps of (i) measuring, using a tilt sensor, data associated a road surface at which the electric bicycle is running to measure a slope value of the road surface, (ii) measuring, using a current sensor, a current that is supplied to an electric motor, (iii) measuring, using a first cadence sensor, a speed of a pedal and (iv) measuring, using a rotary encoder sensor, a speed of the electric motor; (b) receiving an assist level selected by a rider using a control knob of the electric bicycle, and the sensed data from the sensor unit; (c) determining, by employing a filtering technique, a weight of the rider based on the measured slope value of the road surface, the current that is supplied to the electric motor, the speed of the pedal, and the speed of the electric motor; (d) determining a pedal torque based on the measured slope value of the road surface, the current that is supplied to the electric motor, the speed of the pedal, the speed of the electric motor, and the weight of the rider; and (e) determining a motor torque to be provided to the electric bicycle based on the assist level selected by the rider, the measured slope value of the road surface, the current that is supplied to the electric motor, the pedal torque and the weight of the rider for maintaining a torque of the electric bicycle as constant and for improving performance of the electric bicycle.

[0016] The present embodiments provide a constant torque to the electric motor for improving efficiency of the electric bicycle and the mechanical design, assembly and maintenance of the electric bicycle.

[0017] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The embodiments herein will be better understood from the following detailed description with reference to the drawings, in which:

[0019] FIG. 1 illustrates a front view of a mid-drive unit of an electric bicycle according to an embodiment herein;

[0020] FIG. 2 illustrates a side diagram view of a specific gear arrangement of the electric bicycle according to an embodiment herein;

[0021] FIG. 3 illustrates a block diagram of a cadence sensor according to an embodiment herein;

[0022] FIG. 4 illustrates a block diagram of the control unit of the electric bicycle according to an embodiment herein; and

[0023] FIG. 5 illustrates a filtering of the tilt sensor data according to an embodiment herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0025] As mentioned, there remains a need for an electric bicycle with a cost- effective mid-drive unit for high performance and efficiency. The embodiments herein achieved this by providing an electric bicycle that includes a mid-drive unit with specific mechanical design and specific electronic device. Referring now to the drawings, and more particularly to FIGS. 1 through 5, where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments.

[0026] FIG. 1 illustrates a front view of a mid-drive unit of an electric bicycle according to an embodiment herein. The mid-drive unit includes a specific mechanical design and a specific electronic device. The specific mechanical design includes a specific gear arrangement and one or more structural plates 102A-N. The specific gear arrangement includes a first gear 104, a second gear 106, a third gear 108, a fourth gear 110, a first shaft 112 (i.e. a shaft of a pedal), and a second shaft 114 (i.e. a motor shaft of an electric motor). A first gear pair includes the first gear 104 and the second gear 106. A second gear pair includes the third gear 108 and the fourth gear 110. The first gear pair is coupled with the second gear pair to provide gear reduction at two stages to the electric bicycle. The specific gear arrangement is used to provide gear reduction to the electric bicycle and bridge difference between rotating rpm’s of the shaft 112 of a pedal 126 and the motor shaft 114. The mid-drive unit includes a motor 116 to assist a rider to operate the electric bicycle. The motor 116 may be a brushless DC motor. The system lies in the idea of pedal estimation, sensor selection, arrangement, and estimation. The system includes a printed circuit board (PCB) 132.

[0027] The one or more structural plates 102A-N supports the shafts of the specific gear arrangement to improve design, strength, assembly and/or maintenance of the electric bicycle. In an embodiment, the one or more structural plates 102A-N are made of high strength- weight ratio materials. The high strength- weight ratio materials may be composite materials or a steel or an aluminum. A topology of the high strength-weight ratio materials includes (i) at least one of ribs or stiffeners and (ii) bosses for holding bearings.

[0028] The electric bicycle is a pedal assisted electric bicycle. The electric bicycle operates in an assist level set by the rider. There may be several assist level granularities. Generally, these levels vary from 3-5. The assist level is selected by the rider using a control knob. The electric bicycle includes a first clutch 118 and a second clutch 120 to pedal the electric bicycle in desired speed irrespective of the speed of the motor 116 and to eliminate electromotive force that acts as an extra load to the rider. The first clutch 118 is positioned between the shaft 112 of the pedal 126 and a sleeve 133 on which the fourth gear 110 is mounted, which allows the pedal torque coming in at independent speed. The first clutch 118 separates the shaft 112 of the pedal 126 from the rest of the mid-drive unit (e.g. the fourth gear 110 of a gear unit of the mid-drive unit). The second clutch 120 is positioned between the motor shaft 114 and the co-axial shaft, which the second clutch 120 enables coupling or decoupling of the electric motor 116 for running the electric bicycle by electric motor 116. The second clutch 120 separates the motor shaft 114 from the rest of the mid-drive unit (e.g. the first gear 104 of the gear unit of the mid-drive unit). The second clutch 120 is used to operate the electric bicycle in the without assist level.

[0029] The specific electronic device (i.e. a torque maintenance device) includes a sensing unit and a control unit. The sensing unit analyzes or senses the operation of the electric bicycle and communicates information to the control unit to control the operation of the electric bicycle for high performance and efficiency. The sensing unit includes a temperature sensor, a tilt sensor 130, a first cadence sensor 122 and a second cadence sensor or a rotary encoder sensor 124. The temperature sensor senses the temperature of the motor 116 and communicates temperature to the control unit. The temperature of the motor 116 may increase due to the continuous operation of the electric bicycle. In an embodiment, the temperature sensor is positioned in an outer casing of the motor 116. In another embodiment, the temperature sensor is positioned in the surrounding area of the motor 116 inside the mid drive unit.

[0030] The first cadence sensor 122 and the second cadence sensor or a rotary encoder sensor 124 monitor the speed of a pedal 126 and the speed of the motor 116 respectively and communicate to the control unit. In an embodiment, the first cadence sensor 122 is positioned near the pedal 126 of the electric bicycle. In another embodiment, the second cadence sensor or the rotary encoder sensor 124 is positioned near the motor shaft 114. The electric bicycle may operate in at least one of a horizontal surface, upward slope surface, download slope surface or uneven surface. The tilt sensor 130 is positioned in the mid-drive unit and generally, it is mounted on the printed circuit board to obtain data of road surface to measure the slope value. The data obtained using the tilt sensor 130 is communicated to the control unit.

[0031] The control unit obtains the data from the sensing unit and controls the operation of the electric bicycle. The control unit estimates pedal torque and provides motor torque based on the assist level set by the rider. The assist torque levels are approximately ranging from 3-l8Nm for 250W motor. For higher capacity motors, the torque level may be larger. To cool the electric motor, the torque maintenance device includes a cooling unit that is placed inside the mid-drive unit. The cooling unit includes a cooling fan 128 and a temperature sensor. The control unit analyzes the temperature of the motor 116 and switches ON the cooling fan 128 when the temperature is more than a threshold temperature. In one embodiment, the threshold temperature is 150° Celsius. The control unit switches off the cooling fan 128 when the temperature is less than the threshold temperature. The cooling fan 128 is switched ON or switched OFF to utilize battery power efficiently. The control unit determines the pedal torque and weight of the rider and provides one or more feedback signal to provide a motor torque that varies inversely with the pedal torque. The motor torque varies inversely with the pedal torque is achieved using the control unit to provide constant torque to overcome constant load (i.e. the mass of the rider) while operating the electric bicycle.

[0032] The sensing unit and the control unit are positioned away from the motor 116 to minimize data corruption due to electromagnetic interference. The control unit is positioned inside the mid-drive unit. The control knob or any other means to set the assist level is positioned in a handlebar of the electric bicycle. The communication between the control unit and the control knob is performed or established using a wireless communication network. The wireless communication network may be at least one of but not limited to Bluetooth, WIFI, or, etc. In an embodiment, the wireless communication network is made invisible to nearby electric bicycles to ensure safety. In another embodiment, the wireless communication network includes cyber security features. For example, if someone takes the control of controller, she/he may change the controller parameter and untoward accident can happen. Therefore, it needs encryption and password security. The specific torque maintenance device further includes IP65 protection for high durability. The specific torque maintenance device further includes appropriate sensors to provide an overcurrent, an under voltage, and an overvoltage protection.

[0033] FIG. 2 illustrates a side view of the specific gear arrangement of the electric bicycle according to an embodiment herein. The specific gear arrangement includes the first gear 104, the second gear 106, the third gear 108, the fourth gear 110, the shaft 112 of the pedal 126, the motor shaft 114. The first gear pair couples with the second gear pair to provide gear reduction at two stages to the electric bicycle. The gear reduction may range from 6: 1 to 12:1. The gears are coupled between the shaft 112 and the second shaft 114 to operate the electric bicycle using manual efforts obtained from a rider along with the assist level obtained from the motor 116. The first gear 104 is mounted on the second shaft 114 of the motor 116. The second gear 104 and the third gear 106 are mounted on the second shaft/motor shaft 114. The fourth gear 108 is mounted on the sleeve 133 that is coupled with the shaft 112 of the pedal 126 using a first clutch 118. The shaft 112 of the pedal 126 is co axial to an axis of pedal/crank rotation. The second gear 106 and the third gear 108 mounted on a co-axial shaft that is arranged in a specific way to minimize a next axial force generated while operating the electric bicycle.

[0034] For example, this may be done using helical gears and their helical inclination should be in opposite directions, which neutralizes opposite forces. The gears may be made up of composite materials or a steel or an aluminum to minimize the weight of the mid-drive unit. In an embodiment, the gears are the helical type to minimize an acoustic noise and to provide smooth operation while operating the electric bicycle. The electric bicycle includes the cooling fan 128 inside the mid-drive unit to cool the motor 116. The cooling fan 128 may be a blower type fan. The casing includes a closed conduit design for the air circulated by the cooling fan 128 heats up the casing. The motor 116 includes one or more fins on the outside of the casing to provide complete cooling with natural convection.

[0035] FIG. 3 illustrates a block diagram of a cadence sensor according to an embodiment herein. The cadence sensor includes a receiver 302. Six or more magnets 304A-N is positioned on a rotating object (i.e. the crank/disc) in uniform angular position. The cadence sensor senses the speed of the rotating object by monitoring the one or more magnets 304A-N crossing the receiver 302. The one or more magnets 304A-N on crossing the receiver 302 generates a pulse. The pulses are used to find out variation in the speed of the rotating object. The time for generating the pulses is indirectly proportional to the speed of the rotating object.

[0036] FIG. 4 illustrates a block diagram of the control unit of the electric bicycle according to an embodiment herein. The control unit includes a mass estimator 402, a pedal torque estimator 404, a PID (proportional-integral-derivative) controller 408 and a current to torque lookup analyzer 410. The rider mass estimator module 402 estimates the mass of the rider quite accurately using a filtering technique. The pedal torque estimator module 404 estimates the pedal torque. There may be a parametric model of the torque, efforts balance. The parameters are pedal torque, motor torque, and rolling resistance inclination. The pedal torque estimator 404 may be at least one of (i) a Kalman filter (KF), (ii) an Extended Kalman Filter (EKF), (iii) an Unscented Kalman Filter (UKF) or (iv) a Particle Filter.

[0037] The pedal torque estimation provides the estimated pedal torque. The pedal torque is inherently sinusoidal in nature. Therefore, with function“Maximum”, the amplitude of the pedal may be obtained. The block“K” is the function of pedal torque amplitude and “assist level”. With these inputs, block K calculates“Torque setpoint”. The current is measured with a current sensor from electronic circuit 412. This is fed to“torque to current lookup analyzer” 410, to calculate the current torque level the motor is running at. From “Torque setpoint”, the motor torque and estimated pedal torque are subtracted to calculate torque error. This torque error can be positive or negative.“Error torque” will be fed to PID (proportional, Integral and Derivative) controller to calculate the current fed to the motor. If an error is negative then in the next time step, motor torque will come down and if it is positive then torque level will go up.

[0038] The specific electronic circuit 412 includes a current sensor and the tilt sensor 130. The current sensor provides specific current to the motor 116 based on the signal received from the PID controller. The specific current provided to the motor 116 generates required motor torque to operate the electric bicycle with high performance and efficiency.

[0039] In an embodiment, the mass of the rider is estimated. The inputs for mass estimation are a grade of the path measured using the tilt sensor 130, motor torque, pedal cadence measured using cadence sensor 122 and speed of the motor. Lumped parameter torque balance approach is used for calculating the mass of the rider. This is the iterative approach and parameter gets better with the journey. For the next journey, the mass of the rider is stored in a local memory of the control unit to coordinate the operation of the electric bicycle. The control unit further determines the mass of the new rider when the rider changes and coordinates/controls the operation of the electric bicycle. Mass and pedal estimation is an iterative approach. The iteration starts with some assumption and the parameter improves with the journey. These values get stored for the next journey. If the rider is different, these values will not match and the iterative procedure will start again.

[0040] FIG. 5 illustrates a filtering of the tilt sensor data the according to an embodiment herein. The data obtained using the tilt sensor 130 may include noise due to unevenness of the road. Also, the tilt sensor 130 is very sensitive and outputs tilt data every millisecond. But, the speed of the bicycle is very slow (maximum speed of the order of 25- 40kmph) compared to the tilt sensor. The change in road profile the system perceives over at least l0-l5m length. The tilt sensor 130 is also susceptible to vibrations due to small undulations in order of less than a meter distance. Therefore, noise due to vibrations should be filtered out. As well as averaging over several data samples should be done to calculate the grade of the path. The data is averaged or filtered using a noise filter 502 based on averaging parameters to eliminate the noise and obtain the exact slope value of the surface. The averaging parameters include the sampling rate of the tilt sensor 130 and the speed of the electric bicycle. In an embodiment, the tilt sensor 130 provides some non- zero output on the horizontal surfaces. The non-zero output is used as bias to calculate the actual slope value of horizontal surface. In an embodiment, the tilt sensor 130 is used when the efforts from the rider and high assist level are limited/not enough to operate the electric bicycle in the upward slope surface.

[0041] The mid-drive unit utilizes battery power efficiently to coordinate/control the operation of the electric bicycle. The specific torque maintenance device senses both the manual efforts and the slope of the surface traveling and provides required assist level to operate the electric bicycle with high efficiency. The mid-drive unit eases the operation of the electric bicycle in slope surfaces. The specific torque maintenance device increases the performance of the motor 116 by cooling the motor 116 beyond the threshold temperature. The specific mechanical design minimizes the efforts required by the rider.

[0042] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.