Motor system

Abstract

This motor system provides the ability to determine human power output while improving the challenges of sensor placement and cost. [Solution] The motor system comprises a first motor that drives the first wheel, a second motor that drives the second wheel, and a motor control device that torque-controls the first motor and the second motor based on the detection result of a vehicle speed sensor. The motor control device calculates the total acceleration of the human-powered vehicle based on the time change of the vehicle speed detected by the vehicle speed sensor, calculates the motor acceleration of the human-powered vehicle by the first motor and the second motor based on the target torque immediately before each of the first motor and the second motor, calculates the human power output to be input to the input unit based on the difference between the total acceleration and the motor acceleration, and torque-controls the first motor and the second motor so as to generate an assist output determined based on the vehicle speed and the human power output.

Description

Technical Field

[0001] The present invention relates to a motor system.

Background Art

[0002] In recent years, efforts have been made to promote the Sustainable Development Goals (the 2030 Agenda for Sustainable Development, adopted at the United Nations Summit on September 25, 2015 (Heisei 27), hereinafter referred to as "SDGs"). Along with this, technologies aimed at reducing waste and defective products are known in order to ensure sustainable production and consumption patterns.

[0003] Conventionally, a technique for adjusting the power of each of a first motor for assisting the rotation of the front wheel and a second motor for assisting the rotation of the rear wheel based on the human driving force is known (see, for example, Patent Document 1). <9000015>

Prior Art Documents

Patent Documents

[0004] ]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in Patent Document 1, in order to detect the human driving force, a torque sensor for detecting the torque input to the pedal and a cadence sensor for detecting the rotational speed of the crankshaft are required. Therefore, there is a problem that there is little space for installing sensors in a small vehicle body, and the cost increases with the installation of sensors.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a motor system capable of specifying human power output while improving the problems of sensor arrangement and cost. [Means for solving the problem]

[0007] To achieve the above objective, the present invention provides a motor system for assisting the driving of a human-powered vehicle comprising a first wheel, a second wheel, an input unit to which human power output for driving the second wheel is input, and a vehicle speed sensor for detecting vehicle speed, wherein the motor system comprises a first motor for driving the first wheel, a second motor for driving the second wheel, and a motor control device for torque-controlling the first motor and the second motor based on the detection result of the vehicle speed sensor, wherein the motor control device calculates the total acceleration of the human-powered vehicle based on the time change of the vehicle speed detected by the vehicle speed sensor, calculates the motor acceleration of the human-powered vehicle by the first motor and the second motor based on the target torque immediately before each of the first motor and the second motor, calculates the human power output to be input to the input unit based on the difference between the total acceleration and the motor acceleration, and torque-controls the first motor and the second motor so as to generate an assist output determined based on the vehicle speed and the human power output. [Effects of the Invention]

[0008] According to the present invention, it is possible to determine human power output while improving the challenges of sensor placement and cost. Other issues, configurations, and effects will be clarified by the following description of embodiments. [Brief explanation of the drawing]

[0009] [Figure 1] This is a side view of an electric assist bicycle according to this embodiment. [Figure 2] This is a block diagram of the motor system according to this embodiment. [Figure 3] This is a flowchart of the motor control process. [Figure 4] This is an example of a torque estimation map. [Figure 5] This figure shows an example of the relationship between vehicle speed and assist ratio. [Modes for carrying out the invention]

[0010] [Configuration of Electric Assist Bicycle 1] Figure 1 is a side view of the electric assist bicycle 1 according to this embodiment. Figure 2 is a block diagram of the motor system 100 according to this embodiment. Hereinafter, assuming that the electric assist bicycle 1 is placed on a horizontal surface, the direction perpendicular to the mounting surface will be referred to as the "up and down direction", the direction including the direction of travel of the electric assist bicycle 1 will be referred to as the "front and back direction", and the direction perpendicular to the up and down direction and the front and back direction will be referred to as the "left and right direction".

[0011] The electric assist bicycle 1 is an example of an electric assist vehicle that uses an electric motor to assist the force applied by the user (hereinafter simply referred to as "user") to pedal 23L and 23R, thereby rotating the front wheel 7F and rear wheel 7B (i.e., driving the electric assist bicycle 1). As shown in Figures 1 and 2, the electric assist bicycle 1 consists of a main body 2 and a motor system 100. The main body 2 is an example of a human-powered vehicle.

[0012] The main body 2 is a bicycle whose propulsion is assisted by the motor system 100. The main body 2 may be an existing bicycle that has been repurposed, or it may be newly designed to accommodate the motor system 100. As shown in Figure 1, the main body 2 mainly comprises a frame 3, a front fork 4, a saddle 5, handlebars 6, a front wheel 7F and a rear wheel 7B (hereinafter, these may be collectively referred to as "wheels 7"), a steering column 8, a pedaling force transmission mechanism 20, and a brake mechanism 30.

[0013] Frame 3 is a component that supports the main body 2's components (4-8, 20, 30). Frame 3 is made of, for example, steel, aluminum alloy, chromium-molybdenum steel, carbon (carbon fiber reinforced plastic), or a combination thereof. Frame 3 mainly consists of, for example, a top tube 11, a down tube 12, a seat tube 13, a head tube 14, a seat stay 15, a chain stay 16, and a bottom bracket shell 17.

[0014] The top tube 11 is connected at its front end to the head tube 14 and at its rear end to the upper end of the seat tube 13, and extends generally in the front-to-back direction. The down tube 12 is connected at its front end to the head tube 14 and at its rear end to the bottom bracket shell 17, and extends diagonally downward and backward. The seat tube 13 is connected at its upper end to the rear end of the top tube 11 and at its lower end to the bottom bracket shell 17, and extends diagonally downward and forward. The seat tube 13 supports the saddle 5 at its upper end so that it can be raised and lowered.

[0015] The head tube 14 is connected to the front ends of the top tube 11 and the down tube 12 and extends diagonally forward and downward. The steering column 8 of the front fork 4 is rotatably inserted through the head tube 14. The steering column 8 supports the handlebars 6 at its upper end. The front fork 4 extends diagonally forward and downward from the head tube 14 and rotatably supports the front wheel 7F at its lower end. As a result, the direction of the front wheel 7F (i.e., the direction of travel of the electric assist bicycle 1) changes when the handlebars 6 are operated by the user. In other words, the front wheel 7F is a steering wheel whose steering angle can be changed (in other words, steerable) by the handlebars 6, and is an example of a first wheel.

[0016] The seat stay 15 has its front end connected to the seat tube 13 and extends obliquely rearward and downward. The chain stay 16 has its front end connected to the bottom bracket shell 17 and extends generally rearward. And the rear wheel 7B is rotatably supported at the connection portion (i.e., the rear end) of the seat stay 15 and the chain stay 16.

[0017] The pedaling force transmission mechanism 20 is a mechanism that transmits the pedaling force (human power torque TH) of a user sitting on the saddle 5 to the rear wheel 7B. The pedaling force transmission mechanism 20 mainly includes, for example, a crankshaft 21, a pair of crank arms 22L and 22R, a pair of pedals 23L and 23R, a drive gear 24, a driven gear 25, and a chain 26. The pedaling force transmission mechanism 20 (more specifically, the pair of pedals 23L and 23R) is an example of an input portion to which the human power torque TH (human power output PH) for driving the rear wheel 7B is input. Also, the rear wheel 7B is a drive wheel that is driven by the pedaling force transmitted by the pedaling force transmission mechanism 20 and is an example of the second wheel.

[0018] The crankshaft 21 extends in the left - right direction and is rotatably supported by the bottom bracket shell 17. The crank arms 22L and 22R have one end connected to both ends of the crankshaft 21 and extend in a direction orthogonal to the crankshaft 21. Also, the pedals 23L and 23R are rotatably attached to the other ends of the crank arms 22L and 22R. The drive gear 24 is attached to the crankshaft 21 and rotates integrally with the crankshaft 21. The driven gear 25 is attached to the rear wheel 7B and rotates integrally with the rear wheel 7B. The chain 26 is looped around the drive gear 24 and the driven gear 25.

[0019] When a user sitting on the saddle 5 steps on the pedals 23L and 23R, the crankshaft 21 rotates together with the drive gear 24 by the stepping force transmitted by the crank arms 22L and 22R. The rotation of the drive gear 24 is transmitted to the driven gear 25 through the chain 26. The driven gear 25 shifts the rotation of the drive gear 24 transmitted through the chain 26 according to the gear ratio of the drive gear 24 and the driven gear 25, and rotates the rear wheel 7B. Note that the pedaling force transmission mechanism 20 may include a plurality of driven gears that rotate integrally with the rear wheel 7B, and a derailleur that switches the driven gear around which the chain 26 is looped from among the plurality of driven gears.

[0020] The brake mechanism 30 is a mechanism that brakes the electric assist bicycle 1 according to the operation of the user. The brake mechanism 30 mainly includes, for example, a pair of brake levers 31L and 31R, a front brake 32, and a rear brake 33.

[0021] The brake levers 31L and 31R are attached to the handle 6. The brake lever 31L is operated by the user's left hand, and the brake lever 31R is operated by the user's right hand. The front brake 32 clamps the rim of the front wheel 7F and brakes the front wheel 7F in response to the operation of the brake lever 31R. The rear brake 33 clamps the rim of the rear wheel 7B and brakes the rear wheel 7B in response to the operation of the brake lever 31L. Note that the front brake 32 and the rear brake 33 may clamp a disk that rotates integrally with the wheel 7 instead of clamping the rim of the wheel 7.

[0022] [Configuration of Motor System 100] As shown in FIGS. 1 and 2, the motor system 100 mainly includes, for example, a front wheel motor 102F and a rear wheel motor 102B (hereinafter, these may be collectively referred to as "wheel motors 102"), and a motor control device 103. The motor system 100 is a system that controls the drive of the front wheel motor 102F and the rear wheel motor 102B using the electric power stored in the battery 101 (power source).

[0023] The front wheel motor 102F is an example of the first motor, and the rear wheel motor 102B is an example of the second motor. However, the rear wheel motor 102B may be the first motor and the front wheel motor 102F may be the second motor.

[0024] Battery 101 stores power to operate the wheel motor 102 and the motor control device 103. Battery 101 may store power supplied from a commercial power source via a cable (not shown), or it may store regenerative power generated by the wheel motor 102. Battery 101 is detachably attached to the upper surface of the down tube 12, for example, as shown in Figure 1. However, battery 101 is not limited to being installed in the position shown in Figure 1, but can be installed at any position on the main body 2.

[0025] The wheel motor 102 is an electric motor driven by power supplied from the battery 101 via the motor control device 103. The wheel motor 102 is driven according to the control of the motor control device 103. The front wheel motor 102F is mounted on the hub of the front wheel 7F, for example, as shown in Figure 1, and rotates the front wheel 7F. Similarly, the rear wheel motor 102B is mounted on the hub of the rear wheel 7B, for example, and rotates the rear wheel 7B.

[0026] The motor control device 103 controls the drive of the wheel motor 102 using power supplied from the battery 101. The motor control device 103 is mounted on the underside of the saddle 5 (more specifically, on the back of the seat post supporting the saddle 5), for example, as shown in Figure 1. However, the motor control device 103 is not limited to being installed in the position shown in Figure 1, and can be installed at any position on the main body 2.

[0027] Furthermore, as shown in Figure 2, the motor control device 103 is composed of, for example, a distribution board 104, a front wheel board 105F, and a rear wheel board 105B. However, the configuration of the motor control device 103 is not limited to the example in Figure 2, and the functions of the distribution board 104, the front wheel board 105F, and the rear wheel board 105B may be integrated onto a single board. Also, the division of roles of the distribution board 104, the front wheel board 105F, and the rear wheel board 105B is not limited to the following example.

[0028] The distribution board 104 estimates the human power output PH [W] input to the pedal force transmission mechanism 20, and determines the assist output PA [W] that the entire motor system 100 can output based on the estimated human power output PH. The distribution board 104 also distributes the assist output PA to the front wheel output PF [W] and the rear wheel output PB [W]. The distribution board 104 then notifies the front wheel board 105F of the front wheel output PF and the rear wheel board 105B of the rear wheel output PB.

[0029] The front wheel circuit board 105F calculates the front wheel target torque TFt [Nm] corresponding to the front wheel output PF notified from the distribution board 104, and torque-controls the front wheel motor 102F to generate the calculated front wheel target torque TFt. In other words, the front wheel circuit board 105F supplies power corresponding to the front wheel target torque TFt from the battery 101 to the front wheel motor 102F.

[0030] The rear wheel circuit board 105B calculates the target rear wheel torque TBt [Nm] corresponding to the rear wheel output PB notified from the distribution board 104, and torque-controls the rear wheel motor 102B to generate the calculated target rear wheel torque TBt. In other words, the rear wheel circuit board 105B supplies power corresponding to the target rear wheel torque TBt from the battery 101 to the rear wheel motor 102B.

[0031] The front wheel board 105F (rear wheel board 105B) adjusts the time ratio (i.e., duty cycle R[%]) of power supplied to the front wheel motor 102F (rear wheel motor 102B) so that the front wheel motor 102F (rear wheel motor 102B) generates the front wheel target torque TFt (rear wheel target torque TBt), for example, by PWM (Pulse Width Modulation) control.

[0032] Furthermore, the front wheel circuit board 105F notifies the distribution board 104 of the calculated front wheel target torque TFt. Similarly, the rear wheel circuit board 105B notifies the distribution board 104 of the calculated rear wheel target torque TBt. Note that in the control cycle immediately after the electric assist bicycle 1 starts moving from a standstill, the front wheel target torque TFt and the rear wheel target torque TBt are 0.

[0033] As an example, the distribution board 104, the front wheel board 105F, and the rear wheel board 105B each include a CPU and memory. Each board (104, 105F, 105B) then performs the processes described later by having the CPU execute a program stored in memory. As another example, each board (104, 105F, 105B) may be implemented by hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). Furthermore, the distribution board 104, the front wheel board 105F, and the rear wheel board 105B are connected to each other so as to be able to communicate bidirectionally, for example, via a CAN (Controller Area Network).

[0034] Furthermore, the motor system 100 according to this embodiment further includes rotation speed sensors 106F and 106B. In addition, a vehicle speed sensor 112 and a weight sensor 114 are connected to the motor system 100. Any known form of sensor can be used for the various sensors (106F, 106B, 112, 114). Also, the various sensors (106F, 106B, 112, 114) can be attached to any position on the electric assist bicycle 1.

[0035] The rotation speed sensor 106F detects the front wheel rotation speed NF [rpm] of the front wheel motor 102F and outputs a rotation speed signal indicating the detected front wheel rotation speed NF to the distribution board 104 and the front wheel board 105F. The rotation speed sensor 106B detects the rear wheel rotation speed NB [rpm] of the rear wheel motor 102B and outputs a rotation speed signal indicating the detected rear wheel rotation speed NB to the distribution board 104 and the rear wheel board 105B. The rotation speed sensors 106F and 106B can be implemented, for example, by rotary encoders attached to the wheel motor 102.

[0036] The vehicle speed sensor 112 detects the vehicle speed V [km / h] of the electric assist bicycle 1 and outputs a vehicle speed signal indicating the detected vehicle speed V to the motor control device 103. For example, the vehicle speed sensor 112 may detect the vehicle speed V of the electric assist bicycle 1 by reading a magnet attached to the front wheel 7F with a sensor attached to the front fork 4. As another example, the vehicle speed sensor 112 may detect the vehicle speed V of the electric assist bicycle 1 based on a position signal received from GPS (Global Positioning Satellite).

[0037] The weight sensor 114 detects the weight of the user riding the electric assist bicycle 1 (hereinafter referred to as "user weight Wu") and outputs a weight signal indicating the detected user weight Wu [kg] to the motor control device 103. The weight sensor 114 can be implemented, for example, by a pressure sensor attached to the saddle 5. However, the motor control device 103 may use a predetermined fixed value instead of the user weight Wu detected by the weight sensor 114, or a value input by the user through an input interface (not shown). In this case, the weight sensor 114 can be omitted.

[0038] [Motor control processing] Figure 3 is a flowchart of the motor control process. Figure 4 is an example of a torque estimation map. Figure 5 is a diagram showing an example of the relationship between vehicle speed and assist ratio. The motor control process is the process of adjusting the output (torque) of the front wheel motor 102F and the rear wheel motor 102B, respectively. The motor control device 103 repeatedly executes the motor control process shown in Figure 3 at predetermined time intervals (control cycles), for example, during the period when the motor system 100 is powered ON (more specifically, when the assist switch is ON).

[0039] First, the distribution board 104 acquires the detected values ​​(detection results) from various sensors (106F, 106B, 112, 114). In this embodiment, the distribution board 104 acquires, for example, the front wheel rotation speed NF detected by the rotation speed sensor 106F, the rear wheel rotation speed NB detected by the rotation speed sensor 106B, the vehicle speed V detected by the vehicle speed sensor 112, and the user weight Wu detected by the weight sensor 114. Then, the distribution board 104 adds the vehicle weight Wm [kg] of the electric assist bicycle 1, which is pre-stored in memory, and the user weight Wu detected by the weight sensor 114 to determine the total weight Wa [kg].

[0040] Next, the distribution board 104 calculates the total acceleration At[m / sec] of the electric assist bicycle 1 based on the time change of the vehicle speed V detected by the vehicle speed sensor 112. 2 The distribution board 104 calculates the total acceleration At by dividing the vehicle speed Vn detected in the current control cycle and the vehicle speed V(n-1) detected in the previous control cycle by the control period t. The total acceleration At is the acceleration of the electric assist bicycle 1 generated by both the human power output PH input to the pedal force transmission mechanism 20 and the assist output PA output from the wheel motor 102.

[0041] Further, the distribution board 104 estimates the estimated torques TFe and TBe [Nm] in the immediately preceding control cycle based on the rotational speeds NF and NB of the wheels 7 detected by the rotational speed sensors 106F and 106B and the front-wheel target torque TFt and the rear-wheel target torque TBt notified from the front-wheel board 105F and the rear-wheel board 105B in the immediately preceding control cycle (S12). The estimated torques TFe and TBe are estimated values of the torques actually generated by the front-wheel motor 102F and the rear-wheel motor 102B in the immediately preceding control cycle. The distribution board 104 estimates the estimated torques TFe and TBe based on, for example, the estimated torque map shown in FIG. 4.

[0042] The estimated torque map is a table (two-dimensional array) that holds estimated values of the torques T11 to T55 actually generated by the wheel motor 102 in association with combinations of the rotational speeds N1 to N5 of the wheel motor 102 and the target torques T1 to T5 of the wheel motor 102. That is, the distribution board 104 according to the present embodiment estimates the estimated torques TFe and TBe based on the combination of the rotational speed and the target torque of the wheel motor 102. The estimated torque map may be common to the front-wheel motor 102F and the rear-wheel motor 102B, or may be provided for each of them. The estimated torque map is stored in the memory in advance.

[0043] When the target torques are the same (for example, T1), the larger the rotational speeds N1 to N5 are, the smaller the estimated torques T11 to T15 (R11 > R12 > R13 > R14 > R15) become. Also, when the rotational speed N is the same (for example, N1), the larger the target torques T1 to T5 are, the larger the estimated torques T11 to T51 (R11 < R21 < R31 < R41 < R51) become. The specific values of the estimated torque map are determined in advance by experiments or simulations.

[0044] However, the method for estimating the estimated torques TFe and TBe is not limited to the example in Figure 4. As another example, the distribution board 104 may estimate the estimated torques TFe and TBe based on the rotational speed N of the wheel motor 102, the target torques TFt and TBt of the wheel motor 102, and the motor temperature of the wheel motor 102. That is, the estimated torque map may be a three-dimensional array that holds the estimated torques corresponding to the rotational speed N of the wheel motor 102, the target torque T of the wheel motor 102, and the motor temperature of the wheel motor 102. Note that if the rotational speed N and target torque T are the same, the estimated torque will decrease as the motor temperature increases. In this case, the motor system 100 further includes a temperature sensor that detects the motor temperature [°C] of the wheel motor 102 (e.g., the housing, coil, and substrate of the wheel motor 102).

[0045] Next, the distribution board 104 calculates the motor acceleration Am [m / sec] based on the estimated torques TFe and TBe estimated in step S12 and the total weight Wa of the electric assist bicycle 1. 2 The calculation is performed (S13). The motor acceleration Am is the acceleration of the electric assist bicycle 1 caused by the assist output PA output from the wheel motor 102. In other words, the motor acceleration Am is the contribution of the wheel motor 102 to the total acceleration At calculated in step S11.

[0046] The distribution board 104 can calculate the motor acceleration Am using, for example, the following equations 1 to 3. The front wheel thrust FF [N] is the thrust of the front wheel 7F by the front wheel motor 102F (first thrust). The rear wheel thrust FB [N] is the thrust of the rear wheel 7B by the rear wheel motor 102B (second thrust). The front wheel radius RF [m] is the radius of the front wheel 7F. The rear wheel radius RB [m] is the radius of the rear wheel 7B. The front wheel radius RF and the rear wheel radius RB may be the same value or different values. The front wheel radius RF and the rear wheel radius RB are stored in memory beforehand. FF=TFe / RF (Formula 1) FB = TBe / RB ... (Equation 2) Am=(FF+FB) / Wa (Formula 3)

[0047] In other words, the distribution board 104 calculates the front wheel thrust FF by dividing the estimated torque TFe by the radius RF. The distribution board 104 also calculates the rear wheel thrust FB by dividing the estimated torque TBe by the radius RB. Furthermore, the distribution board 104 calculates the motor acceleration Am by dividing the sum of the front wheel thrust FF and the rear wheel thrust FB by the total weight Wa. In other words, the distribution board 104 indirectly calculates the motor acceleration Am based on the target torques TFt and TBt of the previous control cycle. As another example, the distribution board 104 may calculate the motor acceleration Am by substituting the target torques TFt and TBt into equations 1 and 2 instead of the estimated torques TFe and TBe. In this case, the rotation speed sensors 106F and 106B and the processing in step S12 can be omitted.

[0048] Next, the distribution board 104 calculates the human power output PH [W] based on the difference between the total acceleration At and the motor acceleration Am (S14). For example, the distribution board 104 can calculate the human power output PH [W] by substituting the vehicle speed V, the total weight Wa, the total acceleration At calculated in step S11, and the motor acceleration Am calculated in step S13 into equation 4. PH=(At-Am)×V×Wa (Formula 4)

[0049] In other words, the distribution board 104 can calculate the human power output PH by multiplying the value obtained by subtracting the motor acceleration Am from the total acceleration At, the vehicle speed V, and the total weight Wa. Thus, the human power output PH calculated in step S14 is not an actual value directly detected by the sensor, but an estimated value calculated using the estimated torques TFe and TBe (or target torques TFt and TBt).

[0050] Furthermore, the distribution board 104 identifies the assist ratio RA corresponding to the vehicle speed V of the electric assist bicycle 1 based on the relationship shown in Figure 5 (S15). The distribution board 104 also determines the assist output PA [W] by multiplying the human power output PH calculated in step S14 by the assist ratio RA (i.e., based on the magnitude of the human power output PH), as shown in Equation 5. The assist output PA is the output generated by the motor system 100. PA=PH×RA (Formula 5)

[0051] As shown in Figure 5, the greater the human power output PH, the greater the assist output PA. Also, the faster the vehicle speed V, the smaller the assist output PA becomes. More specifically, when the vehicle speed V is less than 10 km / h, the assist ratio RA is 2 (i.e., the assist output PA is twice the human power output PH), and between 10 and 24 km / h, the assist ratio RA gradually decreases as the vehicle speed V increases, and when the vehicle speed V is above the assist limit (24 km / h), the assist ratio (i.e., the assist output PA) becomes 0. In other words, the assist output is determined based on the vehicle speed V and the human power output PH.

[0052] Here, the assist output PA has an upper limit set by law. Therefore, in order to prevent the assist output PA determined using the estimated human power output PH from exceeding the upper limit, a margin α may be further multiplied, for example, as shown in Equation 6. The margin α is a value less than 1. The margin α may be a fixed value or a variable value that changes according to the driving state of the electric assist bicycle 1. As an example, the distribution board 104 may make the margin α smaller (closer to 0) as the total acceleration At is larger, and make the margin α larger (closer to 1) as the total acceleration At is smaller. As another example, the distribution board 104 may make the margin α smaller (closer to 0) as the difference between the estimated human power output PH in adjacent control cycles is larger, and make the margin α larger (closer to 1) as the difference between the estimated human power output PH in adjacent control cycles is smaller. PA=PH×RA×α (Formula 6)

[0053] Furthermore, the distribution board 104 distributes the determined assist output PA to the front wheel output PF[W] and the rear wheel output PB[W] (S16). The front wheel output PF is the output generated by the front wheel motor 102F. The rear wheel output PB is the output generated by the rear wheel motor 102B. The distribution board 104 then notifies the front wheel board 105F of the front wheel output PF and the rear wheel board 105B of the rear wheel output PB.

[0054] The distribution board 104 may distribute the assist output PA to the front wheel output PF and the rear wheel output PB at a predetermined distribution ratio d, for example, as shown in equations 7 to 8. The distribution ratio d is a value of 1 or less. The distribution ratio d may be a predetermined fixed value (for example, 0.5) or a variable value that can be input by the user through the input interface. PF = PH × d ... (Equation 7) PB = PH × (1-d) ... (Equation 8)

[0055] As yet another example, the distribution board 104 may distribute the assist output PA such that the front wheel output PF and the sum of the rear wheel output PB and the human power output PH are the same (i.e., the outputs of the front wheel 7F and the rear wheel 7B are the same), as shown in equations 9 to 10. PF=PB+PH (Formula 9) PF + PB = PA ... (Equation 10)

[0056] Next, the front wheel board 105F drives the front wheel motor 102F to output the front wheel output PF notified by the distribution board 104 (S17). More specifically, the front wheel board 105F calculates the front wheel target torque TFt [Nm] by substituting the front wheel output PF and the front wheel rotation speed NF into equation 11, and torque-controls the front wheel motor 102F to generate the calculated front wheel target torque TFt. Similarly, the rear wheel board 105B drives the rear wheel motor 102B to output the rear wheel output PB notified by the distribution board 104 (S18). More specifically, the rear wheel board 105B calculates the rear wheel target torque TBt [Nm] by substituting the rear wheel output PB and the rear wheel rotation speed NB into equation 12, and torque-controls the rear wheel motor 102B to generate the calculated rear wheel target torque TBt. TF = PF / {(NF × 2π) / 60} ... (Equation 11) TB=PB / {(NB×2π) / 60} (Formula 12)

[0057] As a result, the front wheel 7F is driven by the torque output from the front wheel motor 102F, and the rear wheel 7B is driven by the human power torque input to the pedal force transmission mechanism 20 and the torque output from the rear wheel motor 102B. As a result, the electric assist bicycle 1 moves. The rear wheel board 105B also notifies the distribution board 104 of the calculated rear wheel target torque TBt. Similarly, the front wheel board 105F notifies the distribution board 104 of the calculated front wheel target torque TFt.

[0058] [Effects of the Embodiment] According to the above embodiment, since the human power output PH is estimated based on the vehicle speed V and the immediate target torques TFt and TBt, torque sensors and cadence sensors can be omitted. This improves the problem of sensor placement, especially around the pedaling force transmission mechanism 20, which has a complex structure and limited space, and also suppresses the increase in cost of the electric assist bicycle 1.

[0059] Furthermore, according to the above embodiment, the estimation accuracy of the human power output PH can be improved by estimating the estimated torques TFe and TBe actually generated by the wheel motor 102 based on the rotational speeds NF and NB detected by the rotational speed sensors 106F and 106B and the estimated torque map shown in Figure 4. Similarly, the estimation accuracy of the human power output PH can be further improved by calculating the motor acceleration Am and human power output PH based on the user weight Wu detected by the weight sensor 114.

[0060] Furthermore, according to the above embodiment, by calculating the assist output PA using a margin α, it is possible to prevent the assist output PA from exceeding legal limits even when the estimation accuracy of the human power output PH is low. In particular, the aforementioned effects become more pronounced by reducing the margin α in sections where the estimation accuracy of the human power output PH is unstable (typically, acceleration and deceleration sections).

[0061] [Other variations] The electric vehicles to which the motor system 100 can be applied are not limited to the electric assist bicycle 1. As another example, the electric vehicles to which the motor system 100 can be applied may have multiple front wheels 7F and / or rear wheels 7B, or may have a pair of wheels on the left and right sides instead of front wheels 7F and rear wheels 7B. As yet another example, the electric vehicles to which the motor system 100 can be applied are not limited to those that rotate the wheels 7 by assisting the user's pedaling force with the wheel motor 102, but may also be those that run solely on the propulsion force of the wheel motor 102 (e.g., kick scooters, certain small mopeds). Furthermore, the motor system 100 can be applied not only to electric vehicles but also to any device driven by an electric motor (e.g., radiator fans, power windows, electric oil pumps, etc.).

[0062] Embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the described configurations. Furthermore, it is possible to replace some of the configurations of this embodiment with those of other embodiments, and it is also possible to add configurations from other embodiments to the configuration of this embodiment. Moreover, it is possible to add, delete, or replace some of the configurations of this embodiment with those of other embodiments. [Explanation of symbols]

[0063] 1...Electric assist bicycle, 2...Main body, 3...Frame, 4...Front fork, 5...Saddle, 6...Handlebars, 7B...Rear wheel, 7F...Front wheel, 8...Steering column, 11...Top tube, 12...Down tube, 13...Seat tube, 14...Head tube, 15...Seat stay, 16...Chain stay, 17...Bottom bracket shell, 20...Pedaling force transmission mechanism, 21...Crank axle, 22L,22R...Crank arm, 23L,23 R...Pedal, 24...Drive gear, 25...Driven gear, 26...Chain, 30...Brake mechanism, 31L,31R...Brake lever, 32...Front brake, 33...Rear brake, 100...Motor system, 101...Battery, 102B...Rear wheel motor, 102F...Front wheel motor, 103...Motor control device, 104...Distribution board, 105B...Rear wheel board, 105F...Front wheel board, 106F,106B...Rotation speed sensor, 112...Vehicle speed sensor, 114...Weight sensor

Claims

1. A motor system for assisting the driving of a human-powered vehicle comprising a first wheel, a second wheel, an input unit to which human power output for driving the second wheel is input, and a vehicle speed sensor for detecting vehicle speed, A first motor that drives the first wheel, A second motor that drives the second wheel, The system includes a motor control device that controls the torque of the first motor and the second motor based on the detection results of the vehicle speed sensor, The motor control device is Based on the time change of the vehicle speed detected by the vehicle speed sensor, the total acceleration of the human-powered vehicle is calculated. Based on the target torque immediately preceding the first motor and the second motor, the motor acceleration of the human-powered vehicle by the first motor and the second motor is calculated. Based on the difference between the total acceleration and the motor acceleration, the manual power output input to the input unit is calculated. A motor system characterized by torque control of the first motor and the second motor so as to generate an assist output determined based on the vehicle speed and the human power output.

2. In the motor system according to claim 1, The system further includes a rotation speed sensor for detecting the rotation speed of the first motor and the second motor, The motor control device is Based on the estimated torque map that holds the torque associated with each of the multiple combinations of rotational speed and target torque detected by the rotational speed sensor, the estimated torque actually generated by the first motor and the second motor are estimated. A motor system characterized by calculating the motor acceleration based on the estimated torque of the first motor and the second motor, respectively.

3. In the motor system according to claim 2, The motor control device is The estimated torque of the first motor is divided by the radius of the first wheel to calculate the first thrust of the first wheel by the first motor. The estimated torque of the second motor is divided by the radius of the second wheel to calculate the second thrust of the second wheel by the second motor. A motor system characterized by calculating the motor acceleration by dividing the sum of the first thrust and the second thrust by the total weight of the human-powered vehicle.

4. In the motor system according to claim 2, The motor control device is characterized by calculating the human power output by multiplying the value obtained by subtracting the motor acceleration from the total acceleration, the vehicle speed, and the total weight of the human-powered vehicle.

5. In the motor system according to claim 3 or 4, The motor control device is characterized by determining the total weight by adding a predetermined vehicle body weight of the human-powered vehicle and the user weight detected by a weight sensor provided in the human-powered vehicle.

6. In the motor system according to claim 1, The motor control device is The assist output is calculated by multiplying the aforementioned human power output, the assist ratio determined based on the vehicle speed, and a margin. A motor system characterized by changing the margin according to the driving conditions of the human-powered vehicle.

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