WO2015017456A2 - System and method for controlling a pedal electric bicycle - Google Patents

Abstract

The present invention is directed to methods and systems for controlling power-assisted pedal electric bicycles. Each system incorporates at least one control map that defines the dynamic response of a reference model representing desired bicycle velocity in response to the measured pedal torque imparted by the rider. The reference model contains parameters defining the desired properties of the bicycle, including desired mass and drag properties. In one embodiment, the system implements a "pedal centric" control method wherein measured rider-actuated pedal torque and the reference model are used to determine a desired pedal velocity. In another embodiment, the system implements a "wheel centric" control method wherein measured rider-actuated pedal torque and the reference model are used to determine the desired velocity of the wheel coupled to the drive motor. A closed loop velocity servo controls the motor to minimize the error between the desired rotational velocity and actual rotational velocity.

Description

SYSTEM AND METHOD FOR CONTROLLING A PEDAL ELECTRIC BICYCLE CROSS-REFERENCE TO OTHER PATENT APPLICATIONS:

This application claims the benefit of U.S. provisional application no. 61/860,306, filed July 31, 2013, the disclosure of which application is incorporated herein by reference. BACKGROUND TECHNICAL FIELD

The present invention is related to power assisted pedal electric bicycles and, more particularly, to power assisted pedal electric bicycles employing a fixed-ratio hub electric motor or drive motor wherein the bicycle gearing is shared with the pedal drivetrain. The present invention is also related to a method of controlling power assisted pedal electric bicycles. DESCRIPTION OF RELATED ART

Pedal electric bicycles, bicycles having electric assist motors and related bicycle hardware configurations are disclosed in U.S. Patent Nos. 8,634,979, 8,607,647, 8,327,723, 8,065,926, 7,806,006, 7,706,935, 7,386,482, 7,357,209, 6,684,971, 6,626,805, 6,296,072, 6,263,992, 6,131,683 and 5,570,752, and in U.S. Patent Application Publication Nos. 2013/0267376, 2013/0157804, 2012/0303195, 2012/0083957 and 2011/0133542, and in German Patent No. 102011082082, Chinese Patent Nos. 203172841 and 102673720 and in international patent application publication no. WO2014047341. DISCLOSURE OF THE INVENTION:

In one aspect, the present invention is directed to methods for controlling power assisted pedal electric bicycles. In one exemplary embodiment, the power assisted bicycle has a rear drive wheel and means for coupling the rider torque generated at the pedals to the rear drive wheel. The means of coupling rider torque at the pedals to the rear drive wheel includes chain drive systems connecting pedal sprockets to rear sprockets, with optional gearing systems providing multiple rider selectable gear ratios between pedal and rear drive wheel. An electric assist motor is coupled to the front or rear drive wheel either directly or through a fixed or variable ratio transmission. In the embodiment wherein an electric assist motor is coupled to the rear drive wheel, the electric assist motor can optionally couple in a manner that utilizes the same gearing system coupling the pedals to the rear drive wheel. Each embodiment of the present invention comprises means of simultaneous power transmission to the bicycle wheel(s) via the pedals and the electric assist motor.

In another aspect, the present invention is directed to a control system and method for measuring the torque imparted to the drive wheel by the rider alone. The control system incorporates at least one control map that defines the dynamic response of a reference model representing the desired bicycle velocity in response to the measured torque imparted by the rider. The reference model contains parameters defining the desired properties of the bicycle, including desired mass and desired drag properties. In one embodiment, the control system implements a "pedal centric" control method wherein the control system uses measured rider torque and the reference model to determine the desired rotational velocity of either of the bicycle pedals. In another embodiment, the control system implements a "wheel centric" control method wherein the control system uses measured rider torque and the reference model to determine the desired rotational velocity of the wheel coupled to the drive motor. In each embodiment, the control system utilizes a closed loop velocity servo to control the motor to minimize the error between the desired rotational velocity and actual rotational velocity.

Thus, in one embodiment, the present invention is directed to a method for controlling a power assisted, pedal electric bicycle having an electric power assist motor and a rider-actuated pedal mechanism having pedals, the method comprising the steps of:

providing a microcontroller comprising a processing core, a closed loop velocity servo and a memory having stored therein at least one reference model and feed forward term (K_ff), the processing core being programmed to implement signal processing and gear ratio estimation algorithms;

providing a pedal torque signal (T_Pdi) that corresponds to the torque imparted by the rider via the pedals;

utilizing the processing core to define a desired pedal velocity (co_r_pdi) based on the reference model and the pedal torque signal (Τ_ρ(¾);

utilizing the processing core to multiply the desired pedal velocity signal (co_r_Pdi) by a scalar constant in order to scale the desired pedal velocity signal (co_r_pdi) to a desired motor velocity signal (co_r_m);

utilizing the processing core to compute a torque feed-forward term (T_ff) based on the stored feed-forward term (K_ff) and the pedal torque signal (T_pdi);

inputting the desired motor velocity signal (co_r_m), the torque feed-forward term (T_ff) and an actual motor velocity signal (co_m) of the electric power assist motor into the closed loop velocity servo in order to generate a motor current signal (I_m) for input into the electric power assist motor and to minimize the error between the desired motor velocity signal (co_r_m) and the actual motor velocity signal (co_m). In another embodiment, the present invention is directed to a method for controlling a power assisted, pedal electric bicycle having an electric power assist motor and a rider-actuated pedal mechanism having pedals, the method comprising the steps of:

providing a microcontroller comprising a processing core, a closed loop velocity servo and a memory having stored therein at least one reference model and a feed forward term (Kg), the processing core being programmed to implement signal processing and gear ratio estimation algorithms;

providing a pedal torque signal (T_p(ji) that corresponds to the torque imparted by the rider via the pedals;

providing a wheel speed signal (co_whi) that corresponds to the velocity of the driven wheel of the bicycle;

providing a pedal speed signal (co_Pdi) that corresponds to the speed of the pedals;

utilizing the processing core to define a desired pedal velocity signal (a>_r_Pdi) using the reference model and the pedal torque signal (T_Pdi);

utilizing the processing core to execute a gear ratio estimation algorithm on the wheel speed signal (co_whi) and the pedal speed signal (co_Pdi) to generate an estimated pedal drivetrain gear ratio signal (GR_Pdi);

utilizing the processing core to convert the desired pedal velocity (co_r_pdi) to a desired wheel velocity signal (co_r_whi) using the estimated pedal drivetrain gear ratio signal (GR_pdi);

utilizing the processing core to multiply the desired wheel velocity signal (co_r_whi) by a scalar constant in order to scale the desired wheel velocity signal (co_r_w i) to a desired motor velocity signal (co_r_m);

utilizing the processing core to compute a torque feed-forward term (T_ff) based on the stored feed-forward term (¾) and the pedal torque signal (T_pdi); and inputting the desired motor velocity signal (co_r_m), the torque feed-forward term (T_ff) and an actual motor velocity signal (co_m) of the electric power assist motor into the closed loop velocity servo in order to generate a motor current signal (I_m) for input into the electric power assist motor and to minimize the error between the desired motor velocity signal (co_r_m) and the actual motor velocity signal (co_m). In a further embodiment, the present invention is directed to a method for controlling a power assisted, pedal electric bicycle having an electric power assist motor and a rider-actuated pedal mechanism having pedals, the method comprising the steps of:

providing a microcontroller comprising a processing core, a closed loop velocity servo and a memory having stored therein at least one reference model and a feed forward term (Kg), the processing core being programmed to implement signal processing and gear ratio estimation algorithms;

providing a pedal torque signal (T_p(ji) that corresponds to the torque imparted by the rider via the pedals;

providing a wheel speed signal (co_whi) that corresponds to the velocity of the driven wheel of the bicycle;

providing a pedal speed signal (co_pdi) that corresponds to the pedal speed;

utilizing the processing core to process the wheel speed signal (co_whi) and the pedal speed signal (ω_ρ(ιι) with a gear ratio estimation algorithm to generate an estimated pedal drivetrain gear ratio signal (GR_p(ji); utilizing the processing core to convert the pedal torque signal (T_Pdi) into an estimated pedal torque at the driven wheel signal (T_Whi) using the estimated pedal drivetrain gear ratio signal (GR_Pdi);

utilizing the processing core to use the reference model and the estimated pedal torque at the driven wheel signal (T_whi) to define a desired wheel velocity signal (o_r_w i); utilizing the processing core to convert the desired wheel velocity signal (co_r_whi) into a desired pedal velocity signal (co_r_pdi) using the estimated pedal drivetrain gear ratio signal (GR_Pdi);

utilizing the processing core to multiply the desired pedal velocity signal (co_r_pdi) by a scalar constant in order to scale the desired pedal velocity signal (co_r_Pdi) to a desired motor velocity signal (co_r_m);

utilizing the processing core to compute a torque feed-forward term (T_ff) based on the stored feed-forward term (K_ff) and the pedal torque signal (T_Pdi); and inputting the desired motor velocity signal (co_r_m), the torque feed-forward term (T_ff) and an actual motor velocity signal (co_m) of the electric power assist motor into the closed loop velocity servo in order to generate a motor current signal (I_m) for input into the electric power assist motor and to minimize the error between the desired motor velocity signal (co_r_m) and the actual motor velocity signal (co_m). In another embodiment, the present invention is directed to a power assisted, pedal electric bicycle comprising:

an electric power assist motor;

a pair of wheels, one of which being driven by the electric power assist motor;

a rider-actuated pedal mechanism having pedals; a transducer to measure pedal torque which corresponds to the torque imparted by the rider via the pedals and output a pedal torque signal (T_Pdi);

a transducer to measure wheel speed which corresponds to the velocity of the driven wheel of the bicycle and output a wheel speed signal (co_whi);

a transducer to measure pedal speed and output a pedal speed signal (co_Pdi);

a microcontroller comprising a processing core, a closed loop velocity servo and a memory having stored therein at least one reference model and a feed forward term (K_ff), the processing core being programmed to implement signal processing and gear ratio estimation algorithms, the processing core being further programmed to:

process the wheel speed signal (co_whi) and the pedal speed signal (ω_ρ(π) with a gear ratio estimation algorithm to generate an estimated pedal drivetrain gear ratio signal (GR_pd ;

convert the pedal torque signal (T_Pdi) into an estimated pedal torque at the driven wheel signal (T_whi) using the estimated pedal drivetrain gear ratio signal (GR_Pdi);

define a desired wheel velocity signal (o_r_whi) using the reference model and the estimated pedal torque at the driven wheel signal (T_whi);

multiply the desired wheel velocity signal (oo_r_whi) by a scalar constant in order to scale the desired wheel velocity signal (co_r_w i) to a desired motor velocity signal (co_r_m);

compute a torque feed-forward term (Tff) based on the stored feed-forward term (Kff) and the pedal torque signal (T_pdi); and

input the desired motor velocity signal (co_r_m), the torque feed-forward term (T_ff) and an actual motor velocity signal (co_m) of the electric power assist motor into the closed loop velocity servo in order to generate a motor current signal (I_m) for input into the electric power assist motor and to minimize the error between the desired motor velocity signal (co_r_m) and the actual motor velocity signal (co_m). In another embodiment, the present invention is directed to a method for controlling a power assisted, pedal electric bicycle having an electric power assist motor and a rider-actuated pedal mechanism having pedals, the method comprising the steps of:

providing a microcontroller comprising a processing core, a closed loop velocity servo and a memory having stored therein at least one reference model and a feed forward term (K_ff), the processing core being programmed to implement signal processing and gear ratio estimation algorithms;

providing a pedal torque signal (T_Pdi) that corresponds to the torque imparted by the rider via the pedals;

providing a wheel speed signal (co_whi) that corresponds to the velocity of the driven wheel of the bicycle;

providing a pedal speed signal (co_Pdi) that corresponds to the pedal speed;

utilizing the processing core to process the wheel speed signal (ro_Whi) and the pedal speed signal (co_Pdi) with a gear ratio estimation algorithm to generate an estimated pedal drivetrain gear ratio signal (GR_Pdi);

utilizing the processing core to convert the pedal torque signal (T_Pdi) into an estimated pedal torque at the driven wheel signal (T_Whi) using the estimated pedal drivetrain gear ratio signal (GR_Pdi); utilizing the processing core to use the reference model and the estimated pedal torque at the driven wheel signal (T_whi) to define a desired wheel velocity signal (o_r_w i); utilizing the processing core to multiply the desired wheel velocity signal (oo_r_whi) by a scalar constant in order to scale the desired wheel velocity signal (co_r_whi) to a desired motor velocity signal (co_r_m);

utilizing the processing core to compute a torque feed-forward term (T_ff) based on the stored feed-forward term (¾) and the pedal torque signal (T_pdi); and inputting the desired motor velocity signal (co_r_m), the torque feed-forward term (T_ff) and an actual motor velocity signal (co_m) of the electric power assist motor into the closed loop velocity servo in order to generate a motor current signal (I_m) for input into the electric power assist motor and to minimize the error between the desired motor velocity signal (co_r_m) and the actual motor velocity signal (co_m). BRIEF DESCRIPTION OF THE DRAWINGS :

FIG. 1 is a view of a bicycle configuration comprising an electrically assisted pedal bicycle having an electric assist drive motor connected to the pedal drivetrain, the present invention being applicable to such bicycle configuration;

FIG. 2 is a view of a bicycle configuration comprising an electrically assisted pedal bicycle having an electric assist drive motor integrated into the rear hub, the present invention being applicable to such bicycle configuration;

FIG. 3 is a view of a bicycle configuration comprising an electrically assisted pedal bicycle having an electric assist drive motor integrated into the front hub, the present invention being applicable to such bicycle configuration; FIG. 4A is a block diagram of an electrically assisted pedal bicycle to which the control system and method of the present invention may be applied, the electrically assisted pedal bicycle using a front or rear hub electric assist drive motor directly connected to the load;

FIG. 4B is a block diagram of another electrically assisted pedal bicycle to which the control system and method of the present invention may be applied, the electrically assisted pedal bicycle using a front or rear hub electric assist drive motor connected to the load via a freewheel device;

FIG. 5A is a block diagram of a control system for an electrically assisted pedal bicycle using an electric assist drive motor connected via freewheel to the pedal drive train in accordance with another embodiment of the invention;

FIG. 5B is a block diagram of a control system for an electrically assisted pedal bicycle using an electric assist drive motor connected via freewheel to the pedal in accordance with another embodiment of the present invention;

FIG. 5C is a block diagram of a control system for an electrically assisted pedal bicycle using an electric assist drive motor directly connected to the pedal in accordance with a further embodiment of the present invention;

FIG. 6 is a schematic diagram of a pedal centric control system for electrically assisted pedal bicycles having an electric assist drive motor connected to the pedal drivetrain in accordance with another embodiment of the present invention;

FIG. 7 is a schematic diagram of a pedal centric control system for electrically assisted pedal bicycles having an electric assist drive motor integrated in the front or rear wheel hubs in accordance with a further embodiment of the present invention;

FIG. 8 is a schematic diagram of a wheel centric control system for electrically assisted pedal bicycles having an electric assist drive motor connected to the pedal drivetrain in accordance with another embodiment of the present invention;

FIG. 9 is a schematic diagram of a wheel centric control system for electrically assisted pedal bicycles having an electric assist drive motor integrated in the front or rear wheel hubs in accordance with another embodiment of the present invention;

FIG. 1 OA is a block diagram of a reference model that uses desired mass and damping terms in accordance with one embodiment of the present invention;

FIG. 1 OB is a block diagram of a reference model that uses decoupled static gain and dynamics in accordance with another embodiment of the present invention;

FIG. 1 1 is a view of an exemplary control map for a pedal centric control method in accordance with one embodiment of the present invention; and

FIG. 12 is a view of an exemplary control map for a wheel centric control method in accordance with another embodiment of the present invention. DISCLOSURE OF THE BEST MODES OF THE INVENTION:

As used herein, the terms "drive motor", "electric assist drive motor", "electric assist motor" and "electric power assist motor" have the same meaning and are used interchangeably.

Referring to FIG. 1, there is shown an exemplary bicycle configuration that represents one of many bicycle configurations to which the present invention may apply. Bicycle 1 utilizes an electric assist motor connected to the pedal drive train and is referred to as a "crank drive" configuration. Bicycle 1 includes structural frame 2, seat 3, handle bar 4, rear driven wheel 5 and front wheel 6. The driven wheel incorporates gearing unit 9 that may be comprised of a hub based gear mechanism or a conventional derailleur system. Bicycle 1 also incorporates a chain ring 7. Two cranks 8 are attached to chain ring 7 on opposite sides of bicycle 1 and in a conventionally apposed fashion. One pedal 12 is mounted to the end of each crank 8. The chain 10 couples chain ring 7 to driven wheel 5 via rear wheel gearing unit 9. Electric assist drive motor 11 drives the rear wheel 5 through gearing unit 9. Thus, bicycle 1 demonstrates an electric assist drive motor 11 that couples to the gearing unit 9 through the chain 10. User interface module 13 contains visual and/or audible indicators and tactile pushbuttons for the control and monitoring of the control system of the present invention. User interface module 13 can be mounted on handle bars 4 or other suitable locations on bicycle 1. A variation of the bicycle configuration of FIG. 1 is wherein the electric assist drive motor couples to the gearing 9 via the chain ring 7. Such a variation is represented by the diagram in FIG. 5B.

Referring to FIG. 2, there is shown another bicycle configuration to which the present invention may apply. Bicycle 14 incorporates an electric assist motor integrated in the rear wheel hub and is referred to as a "rear hub drive" configuration. The driven wheel incorporates gearing unit 9 that may be comprised of a hub-based gear mechanism or a conventional derailleur system. Bicycle 14 includes chain ring 7. Two cranks 8 are attached to chain ring 7 on opposite sides of bicycle 14 and in a conventionally apposed fashion. One pedal 12 is mounted to the end of each crank 8. Chain 10 couples chain ring 7 to driven wheel 5 via rear wheel gearing unit 9. Bicycle 1 4 has electric assist drive motor 15 incorporated into the rear wheel hub and drives rear wheel 5 directly with or without reduction gearing.

Referring to FIG. 3, there is shown another bicycle configuration to which the present invention may apply. Bicycle 16 incorporates an electric assist drive motor integrated in the front wheel hub and is referred to as a "front hub drive" configuration. The rear wheel incorporates gearing unit 9 that may be comprised of a hub-based gear mechanism or a conventional derailleur system. Bicycle 16 also incorporates chain ring 7. Two cranks 8 are attached to the chain ring 7 on opposite sides of bicycle 16 in a conventionally apposed fashion. One pedal 12 is mounted to the end of each crank 8. Chain 10 couples chain ring 7 to driven wheel 5 via rear wheel gearing unit 9. Electric assist drive motor 17 is incorporated in the front wheel hub and drives front wheel 6 directly with or without reduction gearing. Referring to FIGS. 4A and 4B, there are shown diagrams of hardware configurations of pedal-type electric bicycles to which the control system and method of the present invention may be applied. These pedal-type electric bicycles can utilize front or rear hub drive motors. The nomenclature used in FIGS. 4 A and 4B is as follows: PDL: rider actuated pedal mechanism CHN: pedal drive train including chain ring and chain GR: gear ratio (may include directly coupled devices with gear ratio 1 : 1) FW: freewheel LOAD: bicycle load comprised of inertial load, drag, road and bike friction, and gravity MTR: electric assist motor The arrows shown in FIGS. 4A and 4B indicate possible directions of power flow. A single- ended ended arrow indicates uni-directional power flow in the direction of the arrow and a double-ended arrow indicates bi-directional power flow in either direction. In the hardware configuration shown in FIG. 4A, the front or rear hub drive motor connects to the load without a freewheel device. Also shown in hardware configuration of FIG. 4A is the pedal drivetrain through which the rider can provide power to the load (for bicycle propulsion) totally independent of and simultaneously with the electric assist motor. The pedal drivetrain in this case includes the pedal mechanism (PDL) in series with a gear ratio (GR) and freewheel (FW). The gear ratio (GR) has at least one and possibly more rider selectable gears. The order of the freewheel (FW) and gear ratio (GR) are a function of the type of gearing system employed on the bicycle and may be interchanged so that freewheel (FW) is before the gear ratio (GR) in other hardware configurations of the present invention. The electric assist motor (MTR) connects directly to the load (LOAD) via the gear ratio (GR). As there is no freewheel in the connection between the load (LOAD) and the electric assist motor (MTR), power is able to flow from the load (LOAD) to the electric assist motor (MTR), for example during bicycle deceleration. In addition, the electric assist motor (MTR) is capable of absorbing power developed by the rider via the pedal drivetrain (CHN). The pedal drivetrain (CHN) provides a means by which the rider can provide power to the load (LOAD) (i.e. for bicycle propulsion) totally independent of and simultaneously with the electric assist motor (MTR).

FIG. 4B illustrates a hardware configurations in which the front or rear hub, having the electric assist motor (MTR) integrated therein, connects to the gear ratio (GR) and the gear ratio (GR) connects to the load (LOAD) via a freewheel (FW). This hardware configuration is identical to the hardware configuration shown in FIG. 4A with the exception of the freewheel (FW) in the connection between the electric assist motor (MTR) and the load (LOAD). In the hardware configuration of FIG. 4B, the electric assist motor (MTR) delivers power to the load (LOAD) only and does not absorb load power and/or rider power developed via the pedal drivetrain (CHN). The pedal drivetrain (CHN) provides a means by which the rider can provide power to the load (LOAD) (i.e. for bicycle propulsion) totally independent of and simultaneously with the electric assist motor (MTR).

Referring to FIGS. 5A, 5B and 5C, there are shown diagrams of hardware configurations o f pedal-electric bicycles using electric assist motors that couple to the pedal drivetrain, sharing a part of or all of the elements of the pedal drivetrain. The system and method of the present invention may be applied to the hardware configurations shown in FIGS. 5A, 5B and 5C. The nomenclature used in FIGS. 5 A, 5B and 5C is identical to the nomenclature used in FIGS. 4A and 4B and explained in the foregoing description. FIG. 5A illustrates a hardware configuration in which the electric assist motor (MTR) and rider actuated pedal mechanism (PDL) connects to the pedal drivetrain (CFIN) via freewheel (FW) and gear ratio (GR). Both the rider actuated pedal mechanism (PDL) and the electric assist motor (MTR) can supply power to the pedal drivetrain (CFIN) simultaneously and independently. The pedal drivetrain (CFIN) connects to the load (LOAD) via freewheel (FW) and gear ratio (GR). Gear ratio has at least one, and possibly more, rider selectable gears. FIG. 5B illustrates a hardware configuration in which the electric assist motor (MTR) connects to the rider actuated pedal mechanism (PDL) via freewheel (FW) and gear ratio (GR). The rider actuated pedal mechanism (PDL) connects to the load (LOAD) in identical fashion to the configuration in FIG. 5A. FIG. 5C illustrates a hardware configuration in which the electric assist motor (MTR) directly connects to the rider actuated pedal mechanism (PDL) via gear ratio (GR). The rider actuated pedal mechanism (PDL) connects to the load (LOAD) in identical fashion to the configuration in FIG. 5B. In the hardware configuration in FIG. 5C, the electric assist motor (MTR) is capable of delivering power to and absorbing power from the rider via the rider actuated pedal mechanism (PDL).

As will be explained in the ensuing description, the system and methods of the present invention may be applied to the hardware configurations shown in FIGS. 4 A, 4B, 5 A, 5B and 5C. However, it is to be understood that the system and methods of the present invention may be applied to other hardware configurations not described herein. In each of the hardware configurations shown in FIGS. 4A, 4B, 5A, 5B and 5C, the electric assist motor (MTR) augments power applied at the rider actuated pedal mechanism (PDL) to assist the rider in the propulsion of the bicycle. As will be explained in the ensuing description, the control systems and methods of the present invention provide a means of controlling the electric assist motor (MTR) in response to rider torque developed at the rider actuated pedal mechanism (PDL) and transmitted to the load (LOAD) via the pedal drivetrain (CHN). The present invention provides two different methods for controlling the electric assist motor (MTR) in response to rider torque at the rider actuated pedal mechanism (PDL). The first method is a pedal velocity control method which is referred to herein as the "pedal centric" control method. The pedal centric control method regulates pedal velocity in response to rider torque at the rider actuated pedal mechanism (PDL). The second method is a wheel velocity control method. The wheel velocity control method, referred to herein as the "wheel centric" control method, regulates driven wheel velocity in response to rider torque at the rider actuated pedal mechanism (PDL). In hardware configurations in which the electric assist motor (MTR) directly couples to the rider actuated pedal mechanism (PDL) or load (LOAD), as shown in FIGS. 4 A and 5C, the electric assist motor (MTR) supplies and absorbs power. The ability of the electric assist motor (MTR) to absorb power implies the potential to impose loads on the rider actuated pedal mechanism (PDL) and/or bicycle that exceed the normal loads on the bicycle that result from road friction, wind drag and gravity. It has been found that this ability of the electric assist motor (MTR) to absorb power can be used to create a load on the rider that is independent of the actual bicycle load (LOAD). In accordance with the invention, pedal centric and wheel centric control methods of the present invention utilize the ability of the electric assist motor (MTR) to absorb power to create a load on the rider that is independent of the actual bicycle load (LOAD). Specifically, the pedal centric and wheel centric control methods utilize the ability of the electric assist motor (MTR) to absorb power in order to use the bicycle as a controlled means of exercise independent of the actual loads (LOAD) imposed on the bicycle. This allows the rider to select the desired level of effort (power) to expend as a function of speed, and the pedal centric control method or wheel centric control method controls the electric assist motor (MTR) to maintain the specified rider load independent of the actual bicycle load (LOAD).

The following electronic signals are described in the ensuing description:

Tpdi: measured pedal torque

oo_whi: measured wheel speed

oopdi: measured pedal speed

GRpdi: estimated pedal drivetrain gear ratio

T_Whi: estimated pedal torque at the wheel

co_r_Whi: desired wheel velocity

Q>_r_pd, : desired pedal velocity

K_gr __m: scalar constant

ω_^Γπι: desired motor velocity

Kff: feed-forward term

Tff: torque feed-forward term

I_m: motor current

(o_m: actual motor velocity It is to be understood that these foregoing signals may be analog or digital signals, depending upon the configuration of the transducers, microcontrollers and electric assist motors that are described in the ensuing description of the embodiments of the present invention. Pedal Centric Control Systems And Methods

FIG. 6 illustrates the pedal centric control method of the present invention applied to bicycle hardware configurations having an electric assist motor (MTR) coupled to the pedal drive chain (CHN) or pedal mechanism (PDL). Such bicycle hardware configurations correspond to the bicycle hardware configurations shown in FIGS. 5A, 5B and 5C as well as other similar bicycle configurations not described herein. The pedal centric control system and method regulate pedal velocity in response to rider torque developed at the rider actuated pedal mechanism (PDL). In one embodiment, the pedal centric control system 100 comprises microcontroller or microprocessor 102. Microcontroller 102 comprises a processing core that implements several signal processing functions, arithmetical operations and algorithms.

Microcontroller 102 further comprises at least one memory, analog-to-digital conversion circuitry, digital-to-analog conversion circuitry, signal inputs and outputs and additional circuitry that form a closed loop velocity servo. Pedal torque transducer 104 measures torque imparted by the rider via the pedals (T_p(ji). Transducer 104 may be configured as a magneto-elastic torque transducer, strain gage or similar device. Microcontroller 102 utilizes a stored reference model to define a desired velocity response of the bicycle pedals (co_r_Pdi) based on the measured torque (T_pdi). Examples of reference models are shown in FIGS. 10A and 10B. Microcontroller 102 implements a multiplication function wherein the desired pedal velocity (co_r_p(n) is multiplied by a scalar constant (K_{gr m}) to scale the desired pedal velocity to a desired motor velocity (oo_r_m). The scalar constant (K_{gr m}) represents the known fixed gear ratio that connects the electric assist motor (MTR) to the rider actuated pedal mechanism (PDL). Microcontroller 102 also implements a closed loop velocity servo to control the electric assist motor (MTR) and associated load (consisting of the bicycle drivetrain and road load) to minimize the error between the actual motor velocity (co_m) and the desired motor velocity (oo_r_m). In a preferred

embodiment, microcontroller 102 is configured and programmed such that the velocity servo loop incorporates proportional plus integral compensation, or other suitable dynamic

compensation networks, operating on the velocity error to maintain desired dynamic and steady state response of the actual motor velocity (o_m). In a preferred embodiment, the velocity servo loop also includes a closed loop current control to provide additional control and to further improve performance. Microcontroller 102 has stored therein a feed-forward term (¾) which may be a constant term or a non-linear function of the pedal torque and/or pedal velocity.

Microcontroller 102 computes a torque feed-forward term (T_ff) using the measured pedal torque (T_pdi) and feed-forward term (Kg). The torque feed-forward term (T_ff) is inputted into velocity servo loop and improves the transient response of the pedal velocity. The velocity servo loop outputs motor current (I_m) that is provided to the electric assist motor (MTR). The actual motor velocity (co_m) is fed back to the velocity servo loop. As a result, the electric assist motor (MTR) and velocity servo loop provide indirect control of the pedal velocity via regulation of actual motor velocity (co_m).

Microcontroller 102 may be realized by any one a number of commercially available microcontrollers that may be programmed to implement any of the functions described in the foregoing description and which has sufficient memory and processing speed. Suitable commercially available microcontrollers included, but are not limited to: C2000 Microcontrollers (Texas Instruments)

MSP430 Ultra-Low-Power Microcontrollers (Texas Instruments)

LPC15xx Series Microcontrollers (NXP Semiconductors)

Kinetis KV3x family of microcontrollers (Freescale Semiconductor) dsPIC33FJ16(GP/MC)101/102 Microcontroller (Microchip Technology, Inc.) dsPIC33FJ32(GP/MC)101/102/104 Microcontroller (Microchip Technology, Inc.)

The pedal centric control system and method of the present invention are applied to bicycle hardware configurations wherein the electric assist motor (MTR) is coupled to the pedal drivetrain (CHN) or pedal mechanism (PDL). Such bicycle hardware configurations are shown in FIGS. 5 A, 5B and 5C. In hardware configurations wherein the electric assist motor (MTR) is directly coupled to the pedal drivetrain (CFIN) without freewheel device (FW), as shown in FIG. 5C, control of the actual motor velocity (co_m) provides direct control of pedal velocity. In the configuration of FIG. 5C, the electric assist motor (MTR) provides power to and absorbs power from the pedal drivetrain (CFIN). The ability of the electric assist motor (MTR) to absorb power from the rider permits use of the reference models that represent loads that are totally decoupled from the actual bicycle load (LOAD). In this case, the load imposed on the rider can be higher than the actual bicycle load (LOAD) thereby allowing use of the bicycle as a rider-controlled means of exercise independent of the actual bicycle loads (LOAD).

Referring to FIG. 7, there is shown another embodiment of the pedal centric control system and method of the present invention. Pedal centric control system 200 is configured for bicycle hardware configurations having an electric assist motor that is integrated with the front or rear wheel hubs. Such bicycle hardware configurations correspond to the bicycle hardware configurations shown in FIGS. 4A and 4B, as well as other bicycle hardware configurations not described herein. The pedal centric control system and method illustrated in FIG. 7 is identical to the pedal centric control system and method shown in FIG. 6, with the exception that the desired pedal velocity is controlled by an electric assist motor that is coupled to the front or rear wheel of the bicycle. Thus, indirect control of pedal velocity via motor velocity control requires conversion of the desired pedal speed to wheel speed using the pedal drive train gear ratio. In order to achieve this conversion, the pedal centric control system and method of FIG. 7 includes an algorithm for the calculation of desired motor speed from desired pedal speed for the general case of bicycles having multiple gear ratios. As shown in Figure 7, control system 200 comprises microcontroller or microprocessor 202. Microcontroller 202 may be configured as any one of the foregoing commercially available microcontrollers that is programmed to implement the functions of this embodiment of the pedal centric control method. Pedal torque transducer 204 measures pedal torque and outputs a signal that represents the measured pedal torque (T_Pdi). Wheel speed transducer 206 measures the wheel speed and outputs a signal that represents the measured wheel speed (co_whi). Pedal speed transducer 208 measures pedal speed and outputs a signal that represents measured pedal speed (co_Pdi). Transducer 204 may be configured as a magneto-elastic, strain-gage or similar devices. Transducers 206 and 208 may be configured as magnetic hall-effect switches, magnetic reed switches or similar devices.

Microcontroller 202 implements a gear ratio estimation algorithm to compute the estimated pedal drivetrain gear ratio (GR_p(ji) based on the measured pedal speed (co_pdi) and measured wheel speed (co_whi). Specifically, the gear ratio estimation algorithm computes the ratio of the measured pedal speed (co_Pdi) and measured wheel speed (co_whi). The gear ratio estimation algorithm may also use known characteristics of the gearing on the bicycle in order to select the estimated ratio using a "nearest neighbor" approach. Examples of known bicycle characteristics include the number of gears and the fixed ratios for each gear. Microcontroller 202 utilizes a stored reference model to define a desired velocity response of the bicycle pedals (ro_r_p(ji) based on the measured torque (Tp_di). This stored reference model is the same reference model used in control system 100 described in the foregoing description. Microcontroller 202 uses the computed (GR_Pdi) to scale the desired pedal velocity (ω_Γ_ρ(¾) to a desired wheel velocity (co_r_Whi). Microcontroller 202 then implements a multiplication function wherein the desired wheel velocity (oo_r_whi) is multiplied by a scalar constant (K_{gr m}) to scale the desired wheel velocity (co_r_whi) to a desired motor velocity (co_r_m). The scalar constant (K_{gr m}) represents the known fixed gear ratio which connects the electric assist motor to the wheel mechanism. Microcontroller 202 has stored therein a feed- forward term (K_ff) which may be a constant term or a non-linear function of the pedal torque and/or pedal velocity. Microcontroller 202 computes a torque feed-forward term (T_t-_f) using the feed-forward term (K_ff) and the measured pedal torque (T_p(]i). Microcontroller 202 also implements a closed loop velocity servo that receives the torque feed-forward term (T_ff) and the desired motor velocity (co_r_m). The torque feed-forward term (T_ff) improves the transient response of the pedal velocity. In response, the velocity servo loop outputs motor current (I_m) for input into the electric assist motor (MTR). The velocity servo loop controls the electric assist motor (MTR) and associated load (consisting of the bicycle drivetrain and road load) to minimize the error between the actual motor velocity (oo_m) and the desired motor velocity (co_r_m). Preferably, microcontroller 202 is configured and programmed such that the velocity servo loop incorporates proportional plus integral compensation, or other suitable dynamic compensation networks, operating on the velocity error to maintain desired dynamic and steady state response of the actual motor velocity (co_m). Microcontroller 202 is preferably configured and programmed such that the closed loop velocity servo has a closed loop current control to provide additional control and to further improve performance. The actual motor velocity (co_m) is fed back to the velocity servo loop. As a result, the electric assist motor (MTR) and velocity servo loop provide indirect control of the pedal velocity via regulation of actual motor velocity (co_m). Wheel Centric Control Systems And Methods

Referring to FIG. 8, there is shown one embodiment of the wheel centric control system and method of the present invention. Wheel centric control system 300 is configured for bicycle hardware configurations having an electric assist motor coupled to the pedal drive train. Such bicycle hardware configurations correspond to hardware configurations shown in FIGS. 5A, 5B and 5C, as well as other bicycle configurations not described herein. Wheel centric control system 300 comprises microcontroller or microprocessor 302. Microcontroller 302 may be configured as any one of the foregoing commercially available microcontrollers that is programmed to implement the functions of this embodiment of the wheel centric control method. Pedal torque transducer 304 measures pedal torque and outputs a signal that represents the measured pedal torque (T_Pdi). Wheel speed transducer 306 measures the wheel speed and outputs a signal that represents the measured wheel speed (co_whi). Pedal speed transducer 308 measures pedal speed and outputs a signal that represents measured pedal speed (ω_ρ(1ι). Transducer 304 may be configured as a magneto-elastic, strain-gage or similar devices. Transducers 306 and 308 may be configured as magnetic hall-effect switches, magnetic reed switches or similar devices. Microcontroller 302 implements a gear ratio estimation algorithm to compute the estimated pedal drivetrain gear ratio (GR_Pdi) based on the measured pedal speed (co_Pdi) and measured wheel speed (co_whi). Specifically, the gear ratio estimation algorithm computes the ratio of the measured pedal speed (co_Pdi) and measured wheel speed (co_whi). The gear ratio estimation algorithm may also use known characteristics of the gearing on the bicycle in order to select the estimated ratio using a "nearest neighbor" approach. Examples of known bicycle characteristics include the number of gears and the fixed ratios for each gear. Microcontroller 302 uses the computed estimated gear ratio (GR_pdi) to scale the measured pedal torque (T_pdi) so as to yield an estimated pedal torque at the wheel (T_Whi). Thus, the wheel centric control system 300 converts pedal torque (T_Pdi) to wheel torque (T_w i) for the general case of bicycles with multiple gear ratios. Microcontroller 302 includes a reference model that defines a desired wheel velocity (o_r_whi) of the bicycle driven wheel in response to the estimated pedal torque at the driven wheel (T_Whi). The wheel torque (T_w i) is applied to the reference model in order to generate the desired wheel velocity (co_r_w i). Microcontroller 302 uses the computed pedal to wheel ratio (GR_pdi) to scale the desired wheel velocity (oo_r_whi) to a desired pedal velocity (oo_r_Pdi). Microcontroller 302 then implements a multiplication function which multiplies the desired pedal velocity (co_r_pdi) by a scalar constant (K_gr __m) to yield a desired motor velocity (oo_r_m). The scalar constant (K_{gr m}) represents the known fixed gear ratio which connects the electric assist motor (MTR) to the rider actuated pedal mechanism (PDL). Microcontroller 302 implements a closed loop velocity servo that receives the desired motor velocity (oo_r_m). This feature is described in detail in the ensuing description. Microcontroller 302 has stored therein a feed-forward term (Kg) which may be a constant term or a non-linear function of the pedal torque and/or pedal velocity. Microcontroller 302 computes a torque feed-forward term (T_ff) using the feed-forward term (K_ff) and the measured pedal torque (T_pdi). The torque feed-forward term (Tff) improves the transient response of the pedal velocity. The velocity servo loop receives the torque feed-forward term (Tff). In response to both the torque feed-forward term (T_ff) and desired motor velocity (co_r_m), the velocity servo loop outputs motor current (I_m) for input into the electric assist motor (MTR). The actual motor velocity (co_m) is fed back to the velocity servo loop. The velocity servo loop controls the electric assist motor (MTR) and associated load (consisting of the bicycle drivetrain and road load) to minimize the error between the actual motor velocity (co_m) and the desired motor velocity (co_r_m). Preferably, microcontroller 302 is configured and programmed such that the velocity servo loop incorporates proportional plus integral compensation, or other suitable dynamic compensation networks, operating on the velocity error to maintain desired dynamic and steady state response of the actual motor velocity (co_m). Microcontroller 302 is preferably configured and programmed such that the velocity servo loop has a closed loop current control to provide additional control and to further improve performance. The electric assist motor (MTR) and velocity servo loop provide indirect control of the wheel velocity via regulation of actual motor velocity (co_m).

Referring to FIG. 9, there is shown another embodiment of the wheel centric control system and method of the present invention. Wheel centric control system 400 is configured for bicycle hardware configurations having an electric assist motor that is integrated with the front or rear wheel hubs. Such bicycle hardware configurations correspond to hardware configurations shown in FIGS. 4 A and 4B, as well as other bicycle configurations not described herein. Wheel centric control system 400 comprises microcontroller or microprocessor 402. Microcontroller 402 may be configured as any one of the foregoing commercially available microcontrollers that is programmed to implement the functions of this embodiment of the wheel centric control method. Pedal torque transducer 404 measures pedal torque and outputs a signal that represents the measured pedal torque (T_p(]i). Wheel speed transducer 406 measures the wheel speed and outputs a signal that represents the measured wheel speed (co_whi). Pedal speed transducer 408 measures pedal speed and outputs a signal that represents measured pedal speed (ω_ρ(π). Transducer 404 may be configured as a magneto-elastic, strain-gage or similar devices.

Transducers 406 and 408 may be configured as magnetic hall-effect switches, magnetic reed switches or similar devices. Microcontroller 402 implements a gear ratio estimation algorithm to compute the estimated pedal drivetrain gear ratio (GR_p(ji) based on the measured pedal speed (copdi) and measured wheel speed (co_whi). Specifically, the gear ratio estimation algorithm computes the ratio of the measured pedal speed (ro_Pdi) and measured wheel speed (co_Whi). The gear ratio estimation algorithm may also use known characteristics of the gearing on the bicycle in order to select the estimated ratio using a "nearest neighbor" approach. Examples of known bicycle characteristics include the number of gears and the fixed ratios for each gear.

Microcontroller 402 uses the computed estimated gear ratio (GR_pdi) to scale the measured pedal torque (T_Pdi) so as to yield an estimated pedal torque at the wheel (T_Whi)- Thus, the wheel centric control system 400 converts pedal torque (T_pdi) to wheel torque (T_whi) for the general case of bicycles with multiple gear ratios. Microcontroller 402 includes a reference model that defines a desired wheel velocity (oo_r_whi) of the bicycle driven wheel in response to the estimated pedal torque at the driven wheel (T_Whi). The pedal torque (T_Pdi) is applied to the reference model in order to generate the desired wheel velocity (co_r_w i). Microcontroller 402 then implements a multiplication function which multiplies the desired wheel velocity (oo_r_whi) by a scalar constant ( _{gr m}) to yield a desired motor velocity (oo_r_m). The scalar constant (K_gr __m) represents the known fixed gear ratio which connects the electric assist motor (MTR) to the wheel mechanism. Microcontroller 402 implements a closed loop velocity servo which receives the desired motor velocity (co_r_m). This feature is described in detail in the ensuing description. Microcontroller 402 has stored therein a feed-forward term (K_ff) that may be a constant term or non-linear function of the pedal torque and/or pedal velocity. Microcontroller 402 computes a torque feed- forward term (T_ff) using the feed-forward term (¾) and the measured pedal torque (Τ_ρ(¾). The torque feed-forward term (T_ff) improves the transient response of the pedal velocity. The velocity servo loop receives the torque feed-forward term (T_ff). In response to both the torque feed- forward term T_ff and desired motor velocity (co_r_m), the velocity servo loop outputs motor current (I_m) for input into the electric assist motor (MTR). The actual motor velocity (co_m) is fed back to the velocity servo loop. The velocity servo loop controls the electric assist motor (MTR) and associated load (consisting of the bicycle drivetrain and road load) to minimize the error between the actual motor velocity (co_m) and the desired motor velocity (co_r_m). Preferably,

microcontroller 402 is configured and programmed such that the velocity servo loop incorporates proportional plus integral compensation, or other suitable dynamic compensation networks, operating on the velocity error to maintain desired dynamic and steady state response of the actual motor velocity (co_m). Microcontroller 402 is preferably configured and programmed such that the velocity servo loop has a closed loop current control to provide additional control and to further improve performance. The electric assist motor (MTR) and velocity servo loop provide indirect control of the wheel velocity via regulation of actual motor velocity (co_m). The main difference between the wheel centric control system and method of FIGS. 8 and 9 is that in the system and method of FIG. 9, the output of the reference model, specifically the desired wheel velocity (co_r_whi), is not converted to desired pedal velocity by the pedal to wheel gear ratio (GRpdi).

It is to be understood that if the pedal centric and wheel centric control systems of the present invention are to be retrofitted to an existing bicycle hardware configuration that already has pedal torque transducers, wheel speed transducers and pedal speed transducers, then control systems 100, 200, 300 and 400 may be configured without such transducers. In such a scenario, the microcontroller is wired to the preexisting transducers and electric assist motor. If the bicycle hardware configuration is to be manufactured or assembled as a new bicycle hardware configuration, then the control systems 100, 200, 300 and 400 may be configured to include such transducers.

In alternate embodiments of the present invention, control systems 100, 200, 300 and 400 do not utilize the feed- forward term (¾-) and thus do not compute a torque feed- forward term (T_ff).

The reference model in each of the pedal and wheel centric control systems and methods described in the foregoing description defines the desired velocity response of the pedal mechanism or driven wheel to the rider torque imposed at the pedals. FIG. 10A illustrates one form of reference model that is structured in a manner to permit specification of desired bicycle behavior via inertia (J_m) and damping (B_m) parameters. In FIG. 10A, the reference model input is the measured torque (T_m), and the output of the model is the desired velocity (co r) of the idealized device. The term 1/s represents numerical integration and operates on the model acceleration (codot_r) to generate the desired velocity (co_r). Both the inertial parameter and damping parameter can be adjusted or tuned to yield desired transient and steady state behavior of the reference model. The steady state torque versus velocity characteristics of the reference model illustrated in FIG. 10A are established by the model damping parameter (B_m).

Specifically, in steady state, the reference model behavior is defined by: ω r =— * T The operating power of the reference model can be computed according to: p r = o) r * T =— * T² When the reference model is used in conjunction with the velocity loop as described in the foregoing descriptions of the pedal centric and wheel centric control systems and methods, its net effect is to cause the actual bicycle to mimic the behavior of the reference model, provided that the velocity servo and electric assist motor do not saturate. Thus, the parameters of the reference model permit the behavior of the actual bicycle to be controlled provided that the velocity servo and associated electric assist motor remain unsaturated. The model damping parameter defines the steady state relationship between input torque and speed for the controlled device, i.e., the pedals in the pedal centric control method and the driven wheel in the wheel centric control method. Accordingly, adjustment of the damping parameter can be used to establish the rider imparted torque and power as a function of controlled device velocity. By providing the rider with a mechanism for adjusting the damping parameter of the reference model, the rider can establish a desired steady state torque and power profile as a function of velocity. In the case where the electric assist motor is connected to the pedal drivetrain or driven wheel via a freewheel device, this level of adjustment is limited by the actual load imposed on the bicycle. In other words, if the electric assist motor cannot absorb power from the rider, the rider can use the reference model to establish a desired steady state load level that is limited to the actual load imposed on the bicycle. In configurations in which the electric assist motor is capable of absorbing rider power, the rider can use the reference model to establish a steady state load level that exceeds the actual load on the bicycle.

FIG. 10B illustrates an alternative expression of the reference model that may be used in any of the pedal centric and wheel centric control systems and methods of the present invention. The reference model of FIG. 10A is equivalent to a first order low pass filter with time constant τ and steady state gain defined as: τ = J m

B m

ω r 1

T„ B m

The reference model illustrated in FIG. 10B is composed of a static gain map in series with a unity gain dynamic function. The static gain map is a linear or non-linear control map that defines the desired steady state relationship of the reference model, i.e., the steady state speed as a function of applied torque. The dynamic function represents the dynamic behavior of the reference model, and has unity gain steady state behavior. The dynamic function illustrated in FIG. 1 OB represents a desired response that has first order low pass filter characteristics with time constant "a". In practice, the dynamic function can be configured to represent any desired dynamic behavior of the device. The selection of the reference model to establish the steady state and dynamic behavior of the device must be consistent with the physics and limitations of the device and associated velocity servo. Using the form of reference model illustrated in FIG. 10B, the static gain map can be used to establish the steady state torque and power versus speed relationship of the reference model and the actual bicycle, as described earlier.

FIG. 11 illustrates an exemplary static map for the reference model of a pedal centric control method. The plot of FIG. 11 illustrates bicycle load torque lines at the pedals (dependent axis) versus pedal cadence, i.e. speed (independent axis). The load lines shown represent actual bicycle torque versus speed as a function pedal drivetrain gear for a fixed 0% grade. The exemplary map is for a pedal drivetrain with seven (7) gears, noted in FIG. 11 as Gear 1 though Gear 7. Also shown in FIG. 1 1 are lines of constant bicycle speed, from 0.0 km/hr-30 km/hr. The straight line represents the exemplary reference model static gain map (labeled as "Model SS Operating Line"). The illustrated static gain map represents a linear relationship between pedal torque and speed, identical to the relationship that would be achieved using the reference model of FIG. 10A with constant damping term (B_m). Specifically, in this case the slope of the reference Model Steady State Operating Line is equivalent to the constant damping term (B_m). When used in the pedal centric control systems and methods of the present invention, the static gain map establishes the level of effort required by the rider at a constant (steady state) speed. As illustrated, the rider torque and power output established by the static gain map at 65 rpm cadence is 14.7 nm and 100 watts, respectively. A steady state operating point is defined by cadence (pedal speed), gear and grade. If the steady state load torque exceeds the reference model established torque at a specific operating point, the electric assist motor will supply the balance to torque. If the steady state load torque is less than the reference model established torque at a specific operating point, the electric assist motor must supply a braking torque, i.e., it must absorb some fraction of the rider developed power. If the hardware configuration does not support the ability of the electric assist motor to absorb power, then the operating point is not a legitimate steady state operating point. In this case, in the absence of changing gear or grade, the cadence would change until a stable operating point is achieved.

Referring to FIG. 12, there is shown an exemplary static map for the reference model of the wheel centric control method of the present invention. The plot in FIG. 12 illustrates bicycle load torque lines at the driven wheel (dependent axis) versus wheel speed (independent axis). The load torque lines shown represent actual bicycle torque versus speed for fixed grades of 0%, 2% and 5%. The straight line represents the exemplary reference model static gain map (labeled as "Model SS Operating Line"). The static gain map as shown exhibits a linear relationship between wheel torque and speed, identical to the relationship that would be achieved using the reference model of FIG. 10A with constant damping term (B_m). As described in the foregoing description, the static gain map establishes the level of effort required by the rider at a constant (steady state) speed. As illustrated, the rider torque and power output established by the static gain map at 25 km/hr wheel speed is approximately 4.8 nm and 100 watts, respectively. A steady state operating point in this case is defined by wheel speed and grade. If the steady state load torque exceeds the torque established by the reference model at a specific operating point, the electric assist motor will supply the balance to torque. If the steady state load torque is less than the torque established by the reference model at a specific operating point, the electric assist motor must supply a braking torque, i.e., absorb some fraction of the rider developed power. If the bicycle hardware configuration does not support the ability of the motor to absorb power, then the operating point is not a legitimate steady state operating point. In this case, in the absence of changing grade, the wheel speed would change until a stable operating point is achieved.

In another embodiment, present invention is a power assisted, pedal electric bicycle that comprises an electric assist motor, a rider-actuated pedal mechanism having pedals, a pair of wheels wherein one of the wheels is driven by the electric assist motor, any one of the control systems 100, 200, 300 and 400, and the required transducers.

It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.

Claims

CLAIMS: WHAT WE CLAIM IS:

1. A method for controlling a power assisted, pedal electric bicycle having an electric power assist motor and a rider-actuated pedal mechanism having pedals, the method comprising the steps of:

providing a microcontroller comprising a processing core, a closed loop velocity servo and a memory having stored therein at least one reference model and feed forward term (K_ff), the processing core being programmed to implement signal processing and gear ratio estimation algorithms;

providing a pedal torque signal (T_Pdi) that corresponds to the torque imparted by the rider via the pedals;

utilizing the processing core to define a desired pedal velocity (co_r_pdi) based on the reference model and the pedal torque signal (T_pdi);

utilizing the processing core to multiply the desired pedal velocity signal (co_r_Pdi) by a scalar constant in order to scale the desired pedal velocity signal (co_r_pdi) to a desired motor velocity signal (co_r_m);

utilizing the processing core to compute a torque feed-forward term (Tff) based on the stored feed-forward term (Kff) and the pedal torque signal (T_pdi);

inputting the desired motor velocity signal (co_r_m), the torque feed-forward term (T_ff) and an actual motor velocity signal (co_m) of the electric power assist motor into the closed loop velocity servo in order to generate a motor current signal (I_m) for input into the electric power assist motor and to minimize the error between the desired motor velocity signal (co_r_m) and the actual motor velocity signal (co_m).

2. The method according to claim 1 wherein providing the pedal torque signal (T_p(ji) comprises measuring the pedal torque (T_p(ji).

3. The method according to claim 1 wherein the scalar constant represents a known fixed gear ratio that connects the electric assist motor to the rider-actuated pedal mechanism.

4. The method according to claim 1 wherein the stored feed-forward term (K_ff) is a constant term.

5. The method according to claim 1 wherein the stored feed-forward term (K_ff) is a nonlinear function of pedal torque and/or pedal velocity.

6. The method according to claim 1 wherein the step of inputting the actual motor velocity signal (co_m) into the velocity servo comprises measuring the actual motor velocity (co_m) of the electric power assist motor.

7. A method for controlling a power assisted, pedal electric bicycle having an electric power assist motor and a rider-actuated pedal mechanism having pedals, the method comprising the steps of:

providing a microcontroller comprising a processing core, a closed loop velocity servo and a memory having stored therein at least one reference model and a feed forward term (Kg), the processing core being programmed to implement signal processing and gear ratio estimation algorithms;

providing a pedal torque signal (T_Pdi) that corresponds to the torque imparted by the rider via the pedals;

providing a wheel speed signal (co_whi) that corresponds to the velocity of the driven wheel of the bicycle;

providing a pedal speed signal (ω_ρ(π) that corresponds to the speed of the pedals;

utilizing the processing core to define a desired pedal velocity signal (co_r_pdi) using the reference model and the pedal torque signal (T_pdi);

utilizing the processing core to execute a gear ratio estimation algorithm on the wheel speed signal (co_whi) and the pedal speed signal (co_pdi) to generate an estimated pedal drivetrain gear ratio signal (GR_pdi);

utilizing the processing core to convert the desired pedal velocity (co_r_Pdi) to a desired wheel velocity signal (co_r_w i) using the estimated pedal drivetrain gear ratio signal (GR_pdi);

utilizing the processing core to multiply the desired wheel velocity signal (co_r_w i) by a scalar constant in order to scale the desired wheel velocity signal (co_r_whi) to a desired motor velocity signal (co_r_m);

utilizing the processing core to compute a torque feed-forward term (T_ff) based on the stored feed-forward term (¾) and the pedal torque signal (T_pdi); and

inputting the desired motor velocity signal (co_r_m), the torque feed-forward term (T_ff) and an actual motor velocity signal (co_m) of the electric power assist motor into the closed loop velocity servo in order to generate a motor current signal (I_m) for input into the electric power assist motor and to minimize the error between the desired motor velocity signal (co_r_m) and the actual motor velocity signal (co_m).

8. The method according to claim 7 wherein providing the pedal torque signal (T_p(ji) comprises measuring the pedal torque.

9. The method according to claim 7 wherein providing the wheel speed signal (co_Whi) comprises measuring the wheel speed of the driven wheel of the bicycle.

10. The method according to claim 7 wherein providing the pedal speed signal (ω_ρ(1ι) comprises measuring the pedal speed.

1 1. The method according to claim 7 wherein the scalar constant represents a known fixed gear ratio that connects the electric assist motor to the rider-actuated pedal mechanism.

12. The method according to claim 7 wherein the stored feed-forward term (Kff) is a constant term.

13. The method according to claim 7 wherein the stored feed-forward term (Kff) is a nonlinear function of pedal torque and/or pedal velocity.

14. The method according to claim 7 wherein inputting the actual motor velocity signal (co_m) into the closed loop velocity servo comprises measuring the actual motor velocity (oo_m) of the electric assist motor.

15. A method for controlling a power assisted, pedal electric bicycle having an electric power assist motor and a rider-actuated pedal mechanism having pedals, the method comprising the steps of:

providing a microcontroller comprising a processing core, a closed loop velocity servo and a memory having stored therein at least one reference model and a feed forward term (K_ff), the processing core being programmed to implement signal processing and gear ratio estimation algorithms;

providing a pedal torque signal (T_Pdi) that corresponds to the torque imparted by the rider via the pedals;

providing a wheel speed signal (co_whi) that corresponds to the velocity of the driven wheel of the bicycle;

providing a pedal speed signal (ω_ρ(π) that corresponds to the pedal speed;

utilizing the processing core to process the wheel speed signal (co_whi) and the pedal speed signal (co_Pdi) with a gear ratio estimation algorithm to generate an estimated pedal drivetrain gear ratio signal (GR_pdi);

utilizing the processing core to convert the pedal torque signal (T_Pdi) into an estimated pedal torque at the driven wheel signal (T_w i) using the estimated pedal drivetrain gear ratio signal (GR_Pdi);

utilizing the processing core to use the reference model and the estimated pedal torque at the driven wheel signal (T_whi) to define a desired wheel velocity signal (o_r_w i); utilizing the processing core to convert the desired wheel velocity signal (co_r_whi) into a desired pedal velocity signal (co_r_pdi) using the estimated pedal drivetrain gear ratio signal (GR_pdi); utilizing the processing core to multiply the desired pedal velocity signal (co_r_p(u) by a scalar constant in order to scale the desired pedal velocity signal (co_r_Pdi) to a desired motor velocity signal (co_r_m);

utilizing the processing core to compute a torque feed-forward term (T_ff) based on the stored feed-forward term (K_ff) and the pedal torque signal (T_Pdi); and inputting the desired motor velocity signal (co_r_m), the torque feed-forward term (T_ff) and an actual motor velocity signal (co_m) of the electric power assist motor into the closed loop velocity servo in order to generate a motor current signal (I_m) for input into the electric power assist motor and to minimize the error between the desired motor velocity signal (co_r_m) and the actual motor velocity signal (co_m).

16. The method according to claim 15 wherein providing the pedal torque signal (T_Pdi) comprises measuring the pedal torque.

17. The method according to claim 15 wherein providing the wheel speed signal (co_whi) comprises measuring the wheel speed of the driven wheel of the bicycle.

18. The method according to claim 15 wherein providing the pedal speed signal (co_pdi) comprises measuring the pedal speed.

19. The method according to claim 15 wherein the scalar constant represents a known fixed gear ratio which connects the electric assist motor to the rider-actuated pedal mechanism.

20. The method according to claim 15 wherein the stored feed-forward term (K_ff) is a constant term.

21. The method according to claim 15 wherein the stored feed-forward term (Kg) is a nonlinear function of pedal torque and/or pedal velocity.

22. The method according to claim 15 wherein inputting the actual motor velocity signal (co_m) into the velocity servo comprises measuring the actual motor velocity (co_m) of the electric assist motor.

23. A method for controlling a power assisted, pedal electric bicycle having an electric power assist motor and a rider-actuated pedal mechanism having pedals, the method comprising the steps of:

providing a microcontroller comprising a processing core, a closed loop velocity servo and a memory having stored therein at least one reference model and a feed forward term (K_ff), the processing core being programmed to implement signal processing and gear ratio estimation algorithms;

providing a pedal torque signal (T_Pdi) that corresponds to the torque imparted by the rider via the pedals;

providing a wheel speed signal (co_whi) that corresponds to the velocity of the driven wheel of the bicycle;

providing a pedal speed signal (ω_ρ(π) that corresponds to the pedal speed;

utilizing the processing core to process the wheel speed signal (ro_Whi) and the pedal speed signal (co_Pdi) with a gear ratio estimation algorithm to generate an estimated pedal drivetrain gear ratio (GR_Pdi);

utilizing the processing core to convert the pedal torque signal (T_Pdi) into an estimated pedal torque at the driven wheel signal (T_Whi) using the estimated pedal drivetrain gear ratio signal (GR_Pdi);

utilizing the processing core to use the reference model and the estimated pedal torque at the driven wheel signal (T_whi) to define a desired wheel velocity signal (o_r_w i); utilizing the processing core to multiply the desired wheel velocity signal (oo_r_whi) by a scalar constant in order to scale the desired wheel velocity signal (co_r_w i) to a desired motor velocity signal (co_r_m);

utilizing the processing core to compute a torque feed-forward term (T_ff) based on the stored feed-forward term (¾) and the pedal torque signal (T_Pdi); and inputting the desired motor velocity signal (co_r_m), the torque feed-forward term (T_ff) and an actual motor velocity signal (co_m) of the electric power assist motor into the closed loop velocity servo in order to generate a motor current signal (I_m) for input into the electric power assist motor and to minimize the error between the desired motor velocity signal (co_r_m) and the actual motor velocity signal (co_m).

24. The method according to claim 23 wherein providing the pedal torque signal (T_pdi) comprises measuring the pedal torque.

25. The method according to claim 23 wherein providing the wheel speed signal (co_whi) comprises measuring the wheel speed of the driven wheel of the bicycle.

26. The method according to claim 23 wherein providing the pedal speed signal (ω_ρ(π) comprises measuring the pedal speed.

27. The method according to claim 23 wherein the scalar constant represents a known fixed gear ratio which connects the electric assist motor to the rider-actuated pedal mechanism.

28. The method according to claim 23 wherein the stored feed-forward term (K_ff) is a constant term.

29. The method according to claim 23 wherein the stored feed-forward term (K_ff) is a nonlinear function of pedal torque and/or pedal velocity.

30. The method according to claim 23 wherein inputting the actual motor velocity signal (co_m) into the velocity servo comprises measuring the actual motor velocity (co_m) of the electric assist motor.