Patent Grant
6984949
The present invention relates to electric vehicles. More specifically, the present invention is concerned with a system and method to selectively prevent movements in a direction opposite to the direction intended by the user.
Electric vehicles are well known in the art. They may be of the purely electric or of the hybrid types. They include an electric motor that is mechanically coupled to one or more wheels to selectively force the rotation of the wheel according to commands given by the user.
Many challenges await the electric vehicle industry. Indeed, the driver of conventional combustion engine equipped vehicles has become accustomed to many features thereof that are now part of the “normal driving feelings”.
An object of the present invention is therefore to provide a system and method to selectively prevent movements of an electric vehicle.
More specifically, in accordance with the present invention, there is provided a system for preventing the movements of an electric vehicle in a direction opposite a desired direction comprising:
a controller;
an electric motor connected to and controlled by the controller; the electric motor being linked to at least one wheel of the vehicle;
a sensor associated with the motor to detect rotation thereof; the sensor being connected to the controller to supply angle position data thereto; the sensor being so configured as to detect rotation of the electric motor in the direction opposite the desired direction and supply this data to the controller that, in turn, calculates a torque to be applied by the motor to counteract the undesired rotation of the motor and controls the motor so that this torque is applied.
According to another aspect of the present invention there is provided a system for preventing the movements of an electric vehicle in a direction opposite a desired direction comprising:
a controller;
an electric motor connected to and controlled by the controller; the electric motor being linked to at least one wheel of the vehicle;
a sensor associated with the vehicle to detect a movement in an undesired direction; the sensor being connected to the controller to supply movement data thereto;
the controller being so configured that upon receipt of data from the sensor that the vehicle is moving in the undesired direction, the controller calculates a torque to be applied to the at least one wheel by the motor to counteract the undesired rotation of the motor and controls the motor so that this torque is applied.
According to a third aspect of the present invention there is provided a method for preventing the movements of an electric vehicle in a direction opposite a desired direction; the electric vehicle comprising an electric motor linked to at least one wheel of the vehicle; the method comprising the acts of:
detecting the direction of the desired movement;
detecting a movement of the vehicle in a direction opposite the desired direction;
calculating a torque to be applied by the motor to the at least one wheel to counteract the movement of the vehicle in the undesired direction;
applying the counteracting torque to the at least one wheel via the electric motor.
According to another aspect of the present invention there is provided a method for preventing the movements of an electric vehicle in a direction opposite a desired direction; the electric vehicle comprising an electric motor linked to at least one wheel of the vehicle; the method comprising the acts of:
detecting the direction of the desired movement;
detecting a rotation of the electric motor in a direction opposite the desired direction;
calculating a torque to be applied by the motor to the at least one wheel to counteract the rotation of the motor in the undesired direction;
applying the counteracting torque to the electric motor. It is to be noted that the expression “electric vehicle” is to be construed as encompassing pure electric vehicles, any type of hybrid vehicles where at least one of the wheels is directly or indirectly connected to an electric motor, and the like.
Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.
In the appended drawings:
In a nutshell, the present invention concerns a hill holder that detects movements of the vehicle of the vehicle in an undesired direction and energizes the motor(s) of the vehicle to counteract this unwanted movement. More specifically, when the vehicle is intended to go forward, the backward movements of the vehicle is detected and the motor(s) is so controlled as to prevent this movement. Similarly, when the vehicle is intended to back-up, forward movements is detected and counteracted.
Turning now to
The system 10 includes an electric motor 12 linked to a wheel 14; a sensor 16, incorporated in the motor 12, to detect the rotation of the drive shaft of the motor 12, user controls 17 including a desired direction input device, and a controller 18 linked to the motor 12, to the sensor 16 and to the user controls 17 so as to, among others, control the motor according to the data supplied by the sensor 16 as will be described hereinbelow.
Turning now briefly to
It is to be noted that many different technologies could be used to design the sensors 16 and 16′. Furthermore, the controller 18 could be a dedicated controller or could be part of the main controller of the vehicle.
A method to selectively prevent movements of an electric vehicle according to an embodiment of the present invention will now be described with reference to
Generally stated the method described hereinbelow aims at applying a counteracting torque to at least one wheel of the vehicle when a movement of the vehicle in a direction opposite the desired direction is detected. The torque applied (T) increases with the angle difference between the instantaneous angle sensed (θ) and the reference angle (θinit) until it reaches the maximal holding torque (Tmax) of the motor. At that time the reference angle is recalculated to prevent undesired oscillations as will be described hereinbelow.
Turning now more specifically to
Step 20 is an initialization step. Two main parameters are initialized in this step. First, the constant Δθmax representing the maximal angle that is allowed before the torque reaches Tmax is set. The constant K is calculated by dividing Tmax by Δθmax and will be used as a scaling constant to help determine the increase of the torque applied to the motor with respect to the instantaneous angle measured.
The second step 22 is the determination of the desired direction of the vehicle. This is done via the transmission controls that are part of the user controls 17. The transmission controls are either in a park, forward, neutral or reverse position.
Of course, other methods could be used to determine the desired direction of the vehicle such as, for example, by an algorithm that analyzes past displacements of the vehicle in such way it knows the vehicle desired direction.
It is to be noted that the park position dictates to the present method that no movement is desired. However, a conventional mechanical mechanism (not shown) is usually provided on vehicles and engaged when the transmission is placed in the park position. Optionally, the method of the present invention could be designed to detect any movements of the vehicle when it is in the park position and counteract this eventual movements, thereby improving safety, should the mechanical mechanism fail.
Alternatively, when the transmission is in the park position, the method and system of the present invention could sense any movement and apply a counteracting torque. It is to be noted that the same rules regarding the maximal torque to be applied to the motor applies. A mechanical brake (not shown) would be automatically applied should the maximal holding torque be reached.
On the contrary, when the transmission is in its neutral position, the system and method described herein is not activated since the vehicle should be allowed to move freely.
Step 24 determines if the direction of the vehicle is opposite the desired direction. This is done by sensing the direction of rotation (if any) of the wheel via an internal or external sensor.
Should step 24 be negative the method returns to step 22.
If the direction of the movement is indeed opposite to the desired direction, the reference angle θinit is acquired from the sensor (step 26).
The next steps aim at determining and applying the appropriate torque T to the motor to counteract the movement detected in the undesired direction.
In step 28, once the reference angle θinit is acquired, the sensor acquires the instantaneous angle data (θ) from the sensor to determine the present angular position of the wheel with respect to the θinit and to calculate Δθ according to the equation Δθ=θ−θinit.
The next step 30 is to calculate the torque T to be applied to the motor to oppose the movement in the undesired direction. Many approaches may be taken to determine the torque T.
These approaches may be summarized by making T a function of the constant K and the angle difference Δθ. Therefore:
T=f(K,Δθ)
A simple function would be T=K*Δθ. The torque T to be applied to the motor would therefore increases linearly with the increase of Δθ.
As mentioned hereinabove, in the initialization step 20, the constant K is calculated and stored. As will be understood by one skilled in the art, the constant K is calculated so that when Δθequals Δθmax the torque T equals the maximal holding torque Tmax of the motor when the simple function discussed hereinabove is used.
Before applying the torque T to the motor, step 32 verifies that the torque T, in absolute value, does not exceed the maximal holding torque Tmax. In other words, it can also be viewed as the verification that Δθ, in absolute value, does not exceed Δθmax.
If the verification of step 32 is negative, the torque T is applied to the motor in step 34.
Step 36 then determines if Δθ is still opposite the desired direction. If so, the method loops to step 28 to recalculate Δθ and thus increases the torque T. If not, the method loops to step 22.
If the verification of step 32 is positive, it means that the torque applied to the motor has reached the maximal holding torque Tmax without adequately counteracting the movement of the vehicle in the undesired direction.
To slow down the movement of the vehicle in the direction opposite the desired direction, the maximal holding torque is applied to the motor in step 40. Concurrently, in step 38, the reference angle θinit is moved (see θinit′ in
As will be understood by one skilled in the art, since it is clear that the movement of the vehicle in the direction opposite the desired direction may not be counteracted in the initial Δθmax region, this region is moved to prevent unwanted oscillations of the vehicle. Indeed, it would be unadvisable to try to force the vehicle back to the initial reference angle position θinit.
The maximal holding torque Tmax discussed hereinabove could be set to a constant value, such as the nominal torque of the motor, for example. But Tmax also could be set to a variable value that decreases in time from maximal torque of the motor to zero shown in FIG. 6. This decrease of the Tmax value is interesting since it requires the driver to keep a foot on the brake when the vehicle is stopped in gear, which prevents the driver from leaving the vehicle without previously putting the transmission in the park position.
It is to be understood that the above method has been simplified for concision purpose and that many other steps could be added. For example, should the user change the desired direction via the user controls 17 while the vehicle is moving, the method described above would wait for the vehicle to come to a stop before being activated in the new desired direction.
The skilled artisan in the art will also understand that the torque applied to the wheels does not stop abruptly once the user of the vehicle starts to depress the acceleration pedal. Indeed, the torque applied remains the same until the command supplied via the acceleration pedal requires a torque greater than the torque applied by the method described hereinabove. A smooth transition is therefore obtained.
One skilled in the art will understand that even though the system of
Although the present invention has been described hereinabove by way of preferred embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention as defined in the appended claims.
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