Method for controlling an electric motor of a pedal vehicle

Abstract

The invention relates to a method for controlling an electric motor (10) of a pedal vehicle (1), which electric motor provides multi-level pedalling assistance, characterised in that the assistance level is selected automatically as a function of a force exerted on the pedals (12), such that an increase in the force automatically increases the assistance level, and vice versa, and in that the assistance level is also configured as a function of the pedalling frequency of the cyclist, such that the frequency is between 50 rpm and 70 rpm, preferably between 55 rpm and 65 rpm and even more preferably equal to 60 rpm

Description

Description Title of the invention: Method for controlling an electric motor of a pedal vehicle Technical field

[0001] The invention relates to the technical field of electrically assisted pedal vehicles, such as a bicycle, and in particular to the method of controlling the motor of these vehicles. Prior art

[0002] Various methods for controlling the assistance of pedal-powered electric vehicles, such as bicycles, are known from the prior art. Typically, the assistance has several levels corresponding to the assistance provided by the motor.

[0003] By "assistance level" we mean the torque curve provided by the motor as a function of its driving parameter (generally the pedaling frequency, or the torque exerted by the user of the vehicle).

[0004] Several levels of assistance allow the user, for example, to drive their vehicle with the aim of saving battery power, such as an "ECO" mode in which the maximum torque that the motor can provide is limited. In such a mode, the torque curve is generally gentle, so that the motor's torque response is moderate: even when a pedal is pressed hard, the torque provided increases only gradually and slowly.

[0005] Conversely, a "SPORT" assistance level provides greater maximum torque. In this mode, the torque curve is generally steep, so the engine's torque response is significant: even when lightly pressing a pedal, the torque delivered increases quickly and significantly.

[0006] The level of assistance must be adapted according to the user's needs, depending on the road conditions, or their load. For example, when tackling a hill, the level of assistance required is higher.

[0007] Choosing assistance can have disadvantages, such as the risk of skidding if the assistance is too abrupt, and is unsuitable for the driving conditions (wet road for example).

[0008] Also known is document WO2011 / 154657, in the name of the Applicant, which describes an assistance method.

[0009] Other methods of selecting the assistance level are known and depend on the planned route. This type of method allows for a balance between the level of assistance provided and battery life, but requires first entering the route to be covered, with detailed location and elevation data.

[0010] Generally speaking, some assistance methods deliver too much engine torque at start-up, so that the user feels carried away, propelled beyond their expectations. These sudden accelerations are likely to cause accidents.

[0011] In addition, these sudden accelerations correspond to peaks in the power delivered by the engine, which prematurely consumes the battery and damages electronic components, such as the battery itself and other power electronics components. Statement of the invention

[0012] One of the aims of the invention is to overcome the disadvantages of the interior, by proposing a method for controlling the assistance of an electric vehicle which avoids premature damage to the power electronics.

[0013] Another aim of the invention is to make the use of the vehicle safer.

[0014] Another aim of the invention is to provide a pedal vehicle which guarantees maximum comfort of use.

[0015] To this end, a method has been developed for controlling an electric motor of a pedal vehicle providing pedal assistance at several levels.

[0016] According to the invention, the level of assistance is selected automatically depending on the force exerted on the pedals, so that an increase in the force automatically increases the level of assistance, and vice versa, and the level assistance is also configured according to the cyclist's pedaling frequency, so that the frequency is between 50 rpm and 70 rpm, preferably between 55 rpm and 65 rpm and even more preferably equal to 60 rpm.

[0017] This way, jolts when starting are avoided, because the level of assistance, which depends on the effort on the pedal, systematically starts at its lowest level when the vehicle is stationary.

[0018] Furthermore, adapting the assistance level so as to maintain a pedaling frequency within the indicated ranges is synonymous with maintaining the user's heart rate, without acceleration. Indeed, it has been observed that it is only at higher pedaling frequencies that the user's heart rate accelerates, causing them to sweat, for example.

[0019] The method according to the invention therefore makes it possible to guarantee both: - user safety, by eliminating jolts when starting; and - its comfort, maintaining a reasonable pedaling frequency, avoiding as much as possible the sensation of physical effort.

[0020] In a particular embodiment, the transition from one assistance level to another passes through all the intermediate levels, and preferably the duration of maintenance at each intermediate level is between 0.3 and 2 seconds, preferably between 0.5 and 1 second, for example 0.5 seconds. In this way, the revolution of the assistance level is progressive, without discontinuity, which makes it possible to avoid jolts or over-torque. Even in the event of a difficult start, for example on a hill, the user is not surprised by a torque that is immediately too high, or that increases too quickly, or by jumps.

[0021] To facilitate restarting the motor after braking, the bicycle's brake actuation is detected by a controller, which significantly reduces the power supplied to the motor, but the motor remains supplied with a lower power than that provided during pedal assistance.

[0022] Advantageously, operating a manual control increases the power provided by the engine. This allows the user to benefit from additional momentum, on demand, when a specific need arises.

[0023] The invention also relates to a pedal vehicle, such as an electrically assisted bicycle, comprising a battery, a motor, and a controller controlling the motor and implementing the method according to the aforementioned characteristics.

[0024] So that a vehicle speed of 25 km / h corresponds to a pedaling frequency of between 50 rpm and 70 rpm, the development of the vehicle is between 6 and 8, preferably between 6.5 and 7.5, and even more preferably between 6.9 and 7.1.

[0025] In order to simplify the design of the vehicle, and in particular the kinematic transmission, the engine is arranged on a hub of the rear wheel of the vehicle. Brief description of the drawings

[0026] [Fig.1] is an illustration of a vehicle according to the invention.

[0027] [Fig. 2] is a graph illustrating different profiles of assistance levels. Detailed description of the invention

[0028] The invention essentially relates to a new method for selecting assistance levels for a vehicle (1) with pedals (12) and electrical assistance. The vehicle (1) may be of the type of a bicycle, a velocimane, a tricycle, or even a quad bike. In the remainder of the detailed description, reference will be made to a bicycle (1), without however limiting the scope of the invention.

[0029] Referring to Figure 1, the bicycle (1) comprises a front wheel connected to a rear wheel by a frame, pedals (12) mounted on the frame and connected to the rear wheel by a transmission, a motor (10), a battery (15), a controller (16), a hand control (14), as well as brakes (13).

[0030] The crank axle is fitted with a force sensor (11) or torque sensor. Alternatively, the force sensor could be arranged on the pedal cranks (12), or on the pedals (12) themselves.

[0031] The motor (10), the battery (15), the force sensor (11), the control (14), and the brakes (13) are connected to the controller (16) by any suitable means, preferably by wiring (17) shown diagrammatically in figure 1.

[0032] The method according to the invention consists in that the level of assistance of the electric bicycle (1) is not mainly based on the pedaling frequency of the cyclist compared to the speed of the bicycle (1), but is based on the pedaling effort of the cyclist. That is to say, the harder the cyclist presses on the pedals (12), the higher the level of assistance. Conversely, the lower the effort on the pedals (12), the lower the level of assistance will be.

[0033] This ensures that the assistance provided by the motor (10) is at its maximum when the cyclist's need is at its maximum and he is pushing on the pedals (12), whereas conversely, when the cyclist wants to slow down, or stops, then the assistance level drops. In the case of the cyclist stopping, the force on the pedal (12) being zero, then the assistance level is at its lowest.

[0034] This process ensures that when the bike is started (1), the assistance level is always the first level, so that there are no jolts or excess torque when starting.

[0035] Furthermore, the controller (16) is programmed so that the selection of the assistance level takes into account the cyclist's pedaling frequency, so as to ensure that it remains within a range between 50 and 70 rpm. This pedaling frequency range ensures that the user's heart rate does not increase. Preferably, the pedaling frequency is between 55 rpm and 65 rpm, and even more preferably is 60 rpm.

[0036] The combination of the correlation of the level of assistance to the pedaling effort, as well as the maintenance of the pedaling frequency in the aforementioned ranges makes it possible to obtain an electric bicycle (1) whose assistance is progressive, flexible, without jolts, and comfortable for the user.

[0037] The control (14), preferably arranged on the handlebars of the bicycle (1), and taking the form of a trigger or a push button, allows the user to obtain additional momentum on demand. Indeed, when the control (14) is pressed, the controller (16) controls the motor (10) so that it delivers a power greater than that normally provided by the selected assistance level. This additional momentum allows the user to overcome an obstacle such as a short steepening of a climb, or to obtain a temporary increase in speed when he wishes to join urban traffic.

[0038] The brakes (13) are equipped with sensors, so that their use tells the controller (16) to cut off the power to the motor (10). However, this is not of a total cut-off, insofar as the motor (10) remains supplied with a low power. This power is insufficient to move the bicycle (1), however it makes it easier to restart the motor (10) following braking. The intensity of the current draw on restarting is reduced, which preserves the proper functioning of the power electronics (battery (15), motor (10)).

[0039] Referring to Figure 2, different assistance level curves are proposed. There are always as many assistance levels (for example five), but the transition from one level to another is not calibrated for the same pedal effort values ​​(12).

[0040] An economic profile (ECO) requires more pressure to trigger the transition to a higher assistance level, while a dynamic profile (BOOST) reaches higher assistance levels with less pressure. An intermediate profile (COMFORT) allows a compromise between battery consumption (15) and the level of assistance obtained.

[0041] Starting from the first level of assistance, when the user exerts a significant effort on a pedal (12) and corresponding for example to assistance level number five of the dynamic profile, the level of assistance does not go directly from level one to level five: the level of assistance will pass through each of the intermediate levels, so that the increase in the level of assistance is progressive. Here again, the sensation of jerkiness for the user is avoided.

[0042] To this end, each intermediate assistance level is maintained for a predetermined duration, for example 0.5 seconds. The increase in the assistance level is therefore progressive.

[0043] This gradual transition also helps to avoid voltage peaks within the power electronics.

[0044] The design and kinematics of the bicycle (1) involve a multitude of parameters, such as the number of teeth on the chainring(s), the number of teeth on the sprocket(s), the diameter of the rear wheel of the bicycle (1). The bicycle (1) is nevertheless configured so that its development, that is to say the distance traveled by means of a pedal revolution (12), i.e. between 6 and 8, preferably between 6.5 and 7.5, and even more preferably between 6.9 and 7.1.

[0045] In this way, when the bicycle (1) is traveling at a speed of 25 km / h, then the rotation frequency of the pedals (12) is between 50 rpm and 70 rpm, and more preferably has a value close to 60 rpm. This embodiment makes it possible to simply ensure that the user's heart rate remains around 60 beats per minute and thus avoids discomfort. This embodiment is simple to implement and reduces the complexity of the computer program executed by the controller (16).

[0046] The bicycle (1) and the method according to the invention avoid sudden variations in the control of the motor (10), and therefore avoid power peaks within the power electronics. Current draws are reduced. These characteristics make it possible to increase the life of the battery (15), which represents a long-term saving. In addition, the reduction of power peaks also increases the autonomy of the battery (15).

[0047] Indeed, the fully automatic operation of the assistance level selection prevents the motor (10) from being used outside its most profitable operating ranges. The automatic selection prevents incorrect selection by a novice user. Indeed, an electric motor (10) used at too low a speed does not allow it to provide sufficient torque. This results in inefficient use of the battery (15).

[0048] For an equivalent bicycle (1), the method according to the invention makes it possible to obtain a gain in autonomy of 10% to 30%. This optimized use of the battery (15) can be used to reduce the capacity of the battery (15), at constant autonomy. Beyond the savings made, the reduction in the capacity of the battery (15) is directly synonymous with a reduction in the mass of the battery (15), which is an undeniable advantage in the case of intermodal use of the bicycle (1).

[0049] The optimized steering process allows for a bicycle (1) without a derailleur. This also represents a saving in mass, a reduction and a simplification of maintenance and the design of the bicycle (1).

[0050] Still with the aim of simplifying design and maintenance, the motor (10) is of the rear wheel motor type, which avoids over-stressing the transmission: we therefore avoid the risks of breakage which can occur with a central motor (located at the level of the pedal assembly).

[0051] In conclusion, the method and the bicycle (1) according to the invention make it possible to obtain discreet assistance, imperceptible to the user. The reduction or even elimination of current calls when restarting the motor (10) makes it possible to obtain a smooth, jolt-free and therefore safe restart of the assistance.

[0052] The power delivered is optimal, avoiding delivering excess power, which saves the battery (15).

[0053] Furthermore, the method and the bicycle (1) may be configured differently from the examples given without departing from the scope of the invention, which is defined by the claims.

[0054] Furthermore, the technical characteristics of the different embodiments and variants mentioned above can be, in whole or in part, combined with each other. Thus, the method and the bicycle (1) can be adapted in terms of cost, functionality and performance.

Claims

Claims 1. Method for controlling an electric motor (10) of a pedal vehicle (1) providing multi-level pedaling assistance, characterized in that the level of assistance is automatically selected as a function of a force exerted on the pedals (12), so that an increase in the force automatically increases the level of assistance, and vice versa, and in that the level of assistance is also configured as a function of the pedaling frequency of the cyclist, so that the frequency is between 50 rpm and 70 rpm, preferably between 55 rpm and 65 rpm and even more preferably equal to 60 rpm.

2. Method according to claim 1, characterized in that the transition from one level of assistance to another passes through all the intermediate levels, preferably the duration of maintenance at each intermediate level is between 0.5 and 1 second, for example 0.5 seconds.

3. Method according to one of the preceding claims, characterized in that when the brakes (13) of the bicycle (1) are actuated, the motor (10) is supplied with a lower power than that supplied during pedal assistance, so as to facilitate restarting of the motor (10) after braking.

4. Method according to one of the preceding claims, characterized in that actuation of a manual control (14) increases the power supplied by the motor (10).

5. Electrically assisted pedal vehicle (1) comprising a battery (15), a motor (10), and a controller (16) controlling the motor (10) and implementing the method according to one of the preceding claims.

6. Vehicle (1) according to claim 5, characterized in that its development is between 6 and 8, preferably between 6.5 and 7.5, even more preferably between 6.9 and 7.

1.

7. Vehicle (1) according to one of claims 5 to 6, characterized in that the motor (10) is arranged on a hub of the rear wheel of the vehicle (1).

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