METHOD OF SYNCHRONIZING ADJUSTMENT OF PEDAL LEVERS IN A STEPPER MOTOR DIRECT DRIVE ADJUSTABLE PEDAL ASSEMBLY

Abstract

A pair of adjustment mechanisms (21, 41) interconnect a support (12) and first (14) and second (34) pedal levers. The adjustment mechanisms (21, 41) adjust the operational position of the pedal levers (14, 34) relative to the support (12). In particular, a stepper motor (52) and screw (32) unit moves the respective pedal levers (14, 34) along rods (28, 48). A controller (56) sends pulses of energy to each of the motors (52), measures a time to reach a predetermined resistance condition of each motor (52) during each pulse, and terminates energy to both motors (52) in response to the time being below a predetermined time period in any pulse to either motor (52), thereby synchronizing the movement of both pedal levers (14, 34).

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject invention generally relates to an adjustable pedal assembly used in a vehicle to vary the operating position of a plurality of foot pedals that mechanically or electrically control various vehicle systems, such as the clutch, brake and throttle systems. More specifically, the subject invention relates to a method of synchronizing adjustment of the foot pedals to ensure that the foot pedals are similarly adjusted.

2. Description of the Prior Art

Typically, adjustable pedal assemblies have used direct current electrical motors to rotate a drive cable that, in turn, rotates a worm gear to adjust the position of the pedal. Examples of such assemblies are shown in U.S. Pat. Nos. 5,632,183; 5,697,260; 5,722,302; and 5,964,125 to Rixon et al., 3,643,524 to Herring, 4,875,385 to Sitrin, 4,989,474 to Cicotte et al. and 5,927,154 to Elton et al. Other assemblies eliminate the cable and connect the worm gear more directly to the pedal lever, as illustrated in U.S. Pat. Nos. 6,205,883 to Bortolon and 6,151,984 to Johansson et al. In order to stay within cost limitations, these assemblies require a relatively large number of parts, are noisy and imprecise in output. They also present difficult packaging parameters.

Strict standards have been developed in regard to the position of the brake pedal relative to the position of the accelerator pedal, i.e., the synchronization of adjustment of the brake and accelerator pedals. Some assemblies address this requirement by using one motor to drive the adjustment of both pedals, as shown in the aforementioned U.S. Pat. No. 5,722,302.

SUMMARY OF THE INVENTION AND ADVANTAGES

The subject invention provides a method of synchronizing adjustment of first and second pedal levers with first and second stepper motors. The method includes sending pulses of energy to each of the motors and measuring a time to reach a predetermined resistance condition of each motor during each pulse. Energy to the motors is terminated in response to the time being below a predetermined time period in any pulse to either motor.

Accordingly, adjustable movement of the respective pedal levers is synchronized by shutting down electrical energy to both motors in the event one of the motors becomes stalled as evidenced by the time to reach the predetermined resistance condition. Such a time period is measured in milliseconds thereby preventing the motors and pedal adjustment from coming out of synchronization.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view from the left of a preferred embodiment;

FIG. 2 is a perspective view from the right of the preferred embodiment;

FIG. 3 is an enlarged side view showing the motors and pedal levers;

FIG. 4 is a perspective view of the motor and drive control;

FIG. 5 is a perspective view of a controller of the subject assembly;

FIG. 6 is schematic view of the controller and motors;

FIG. 7 is a graph showing the voltage timing;

FIG. 8 is a plot of kick-in times versus current and voltages in each pulse of energy sent to a stepper motor for a no load condition of the motor;

FIG. 9 is a plot like FIG. 8 but showing a motor loaded condition; and

FIG. 10 is a plot like FIGS. 8 and 9 but showing a stalled condition where the time required in one pulse for the running current to reach a preset limit is much less than a normal running condition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, an adjustable pedal assembly is generally shown at 10 in FIGS. 1 and 2. A support, generally indicated at 12, is included for mounting the assembly to a vehicle structure.

A first pedal lever 14 is pivotally supported for rotation about an operational axis A with respect to the support 12. The support 12 comprises a bracket having side flanges 16 and 18 that rotatably support a shaft 20. A first adjustment mechanism, generally indicated at 21, interconnects the support 12 and the pedal lever 14 for adjusting the operational position of the pedal lever 14 relative to the operational axis (A) between a plurality of adjusted positions. More specifically, the shaft 20 supports a first arm 22. A link 24 depends from the shaft 20 and supports an attachment 26 that connects to the vehicle system for operating a system thereof, e.g., a brake system. As is well known in the art, anyone of the shaft 20, arm 22 or link 24 could be connected to an electrical sensor for sending an electrical signal to a vehicle system instead of a mechanical output. The first adjustment mechanism also includes a guide, in the form of a rod 28, movably supported by the support 12, and the pedal lever 14 includes a collar 30 that is slidably supported by the rod 28. The rod 28 is hollow and a nut (not shown) is moved axially within the rod 28 by a screw 32, as shown in FIG. 4. Such an assembly is illustrated in the aforementioned U.S. Pat. Nos. 5,722,302 and 5,964,125. However, as will be appreciated, the guide may take the form of a plate that slidably supports the pedal lever, the plate being either slidable or rotatable relative to the support.

The assembly 10 also includes a second pedal lever 34 pivotally supported for rotation about a second operational axis B with respect to the support 12. The bracket defining the support 12 includes an ear 36 that supports a pin 38. A second adjustment mechanism, generally shown at 41, interconnects the support 12 and the second pedal lever 34 for adjusting the operational position of the second pedal lever 34 relative to the second operational axis B between a plurality of adjusted positions. The second adjustment mechanism includes a second arm 42 pivotally supported by the pin 38. The upper end 44 of the second arm 42 is bifurcated to connect to a control cable, but as set forth above, the output may be electrical instead of mechanical. Again, the second adjustment mechanism 41 includes a guide, in the form of a rod 48, movably supported by the support 12, and the second pedal lever 34 includes a collar 50 that is slidably supported by the rod 48. The rod 48 is hollow and a nut (not shown) is moved axially within the rod 48 by a screw 32, as shown in FIG. 4. This screw 32 and nut arrangement can be like that shown in the aforementioned Rixon et al patents.

The assembly 10 is characterized by each of the mechanisms 21 and 41 including an electrically operated motor 52 for sequentially moving in increments of movement. Such a motor 52 indexes when energized in a programmed manner. The normal operation consists of discrete angular motions of uniform magnitude rather than continuous motion. A shown in FIG. 6, each motor 52 includes a plurality of windings 54. Each motor 52 has a housing surrounding the motor 52 and the screw 32 extends from the housing whereby the screw 32 and motor are a compact and universal unit. A motor housing is attached to the respective ends of the rods 28 and 48 with the screw 32 thereof extending into the associated rod 28 or 48 for moving the pedal levers 14 and 34 between the adjusted positions. It is important that the motor 52 be connected directly to the screw 32, i.e., that the screw 32 extends out of and is supported by the housing surrounding the motor 52. No loads from the operator to the pedal lever occur during the adjustment and the force required to move the collars 30 and 50 along the rods 28 and 48 is relatively low. However, the collars 30 and 50 cock or tilt relative to the axis of the rods 28 and 48 in response to a force on the pedal pads 68 or 70. This tilting or cocking locks the collar 30 and/or 50 to the associated rod 28 or 48 whereby the force is transferred to the support 12 and not to the motor/screw 52/32 unit.

As shown in FIG. 6, a controller 56 is included for sending pulses of electrical energy sequentially to the windings 54 to incrementally rotate the motor 52 through a predetermined angle in response to each pulse. Each motor 52 includes a drive circuit 58 interconnecting the controller 56 and the respective drives 58, which, in turn, energize the windings 54. The controller 56 includes a memory, generally shown at 60 in FIG. 6, for summing the pulses to keep track of the operational position of the pedal lever 14 in all adjusted positions. The controller 56 also includes a timer 62 for measuring the time to reach a predetermined pulse width modulation sufficient to rotate the motor 52. Attendant to this, the controller 56 includes latches each of which includes a voltage meter 64 for determining the voltage applied during the measured time to reach the predetermined pulse width modulation. The controller 56 includes a coordinator 66 for measuring the time to reach the predetermined pulse width modulation to alter the pulses of electrical energy to move the pedal lever 14 to the desired operational position in response to the time being outside a predetermined limit. In order to prevent the effects of the stall of a motor 52, thereby adversely affecting the desired or programmed position of the pedal lever, the controller 56 detects a stall and adjusts the pedal lever position or shuts down the system. When each winding 54 of a motor 52 is energized, the current sent to the motor 52 rises until a pulse width modulation (PWM) set point is reached. The time from energizing the winding to reaching the PWM set point is based on the voltage applied to the winding and any load on the system. As shown in FIG. 7, a stalled motor 52 differs from a properly operating motor 52 by the measured time from energization of the windings to reaching PWM set point, the measured time for a properly operating motor being approximately twice the measured time for a stalled motor. Accordingly, the controller 56 measures the time and voltage to detect a stall, and when one occurs, corrects to reposition the motor to the programmed position. In addition, the controller 56 includes a software program for adjusting the respective operational positions of the first 14 and second 34 pedal levers in a predetermined relationship to one another.

In order to accumulate the data depicted in FIG. 7, a series of tests are run on a stepper motor 52 wherein the controller 56 sends pulses of electrical energy sequentially to the windings 54 of the motor 52. Various different voltages (labeled OUT1A Voltage on the left of each of FIGS. 8-10 and on the x axis of FIG. 7) are applied. The current is represented by measuring the voltage across a resistor (labeled R_S Voltage on the right of each Figure). Each Figure shows one full pulse and the beginning of a second pulse.

The controller 56 includes one or two pulse width modulators (PWM) for receiving each pulse of electrical energy for oscillating that energy at a very high frequency in each pulse to the windings of the stepper motors 52. The plot in FIG. 8 is a result of applying a voltage in each pulse and without a load on the motor 52. The bottom of FIGS. 8-10 presents a scale of time in milliseconds for the PWM to reach its operating modulation, i.e., kick-in timing, which is about 0.006 seconds (6 milliseconds) in FIG. 8. The kick-in time for a normal load on the motor 52 with the same voltage applied is illustrated in FIG. 9 and is about 0.008 seconds. However, the kick-in time for a stalled motor 52 increases at a much faster rate as illustrated in FIG. 10. In other words, the running current shoots up rapidly when the motor does not turn, which could occur in the over load situation or something jamming operation. As illustrated in FIG. 10, the kick-in time for the stalled motor 52 is about 0.003 seconds.

The kick-in times for each of the no-load and stalled results for various different voltages are plotted on the x axis in FIG. 7. The upper three curves in FIG. 7 represent the normal kick-in times under no load conditions for the various voltages with each curve being at different temperatures. The lower three curves in FIG. 7 represent the kick-in times when the motor is in a stalled condition for the same various voltages and at the same temperatures.

In order to keep the first and second motors 52 in synchronization to synchronize the adjustment of the operational positions of the first 14 and second 34 pedal levers, a curve is drawn between the two sets of curves in FIG. 7 to select a predetermined time period at which the energy to both motors 52 will be terminated. The time to reach a predetermined current, as illustrated in right scale of FIGS. 8-10, is measured by the timer 62 for each motor 52, and should that time period be below the predetermined selected time, i.e., the curve between the two sets in FIG. 7, the controller includes a switch to shut down the electrical energy pulses to the PWM to stop both motors 52. In order to restart, the system must be re-energized as by hitting the start button again. Accordingly, the timer 62 measures the time to reach a predetermined resistance condition of either of the motor windings 54 during each pulse and terminates the energy supply to the windings of both motors in response to that time being below a predetermined time period, thereby preventing the adjustment of the pedal positions from coming out of sychronization.

It is desirable that the pedal levers 14 and 34 be adjusted in unison to accommodate different operators. The controller 56 sending equal and simultaneous signals to the respective motors 52 may accomplish this. However, in some cases where the mounting of the two pedal levers 14 and 34 differ substantially (as is in the embodiment illustrated herein), the controller may send disproportionate signals to the two motors to maintain equal or equivalent movement of the pedal pads 68 and 70 on the lower or distal ends of the respective pedal levers 14 and 34. In any case, the measurement and timing of the resistance indicating a stall will shut down both motors to maintain the adjustment in proportional synchronization. Once the motors are shut down, the operator recognizes a stall or stoppage and relieves foot pressure from the pedal or pedals and re-starts the controller to send pulses to the motors. If the stall condition continues, the system is mechanically locked and maintenance is required, but without damage to the motors.

An electrical connector 72 for the winding 54 extends out of the motor housing. The controller 56 and motor drive 58 are disposed within a separate housing from which extends an electrical connector 74 to connect to an electrical cable which divides and connects to the two motor connectors 72. An additional electrical connector 76 connects to an electrical cable that leads to the vehicle system.

Obviously, many modifications and variations of the subject invention are possible in light of the above teachings. The invention may be practiced otherwise than as specifically described within the scope of the appended claims. The reference numerals in the claims are merely for convenience and are not to be read in any way as limiting.

Claims

1. A method of synchronizing the adjustment of first (14) and second (34) pedal levers with first and second stepper motors (52) by the steps of: sending pulses of energy to each of the motors (52), measuring the time to reach a predetermined resistance condition of each motor (52) during each pulse, and terminating energy to both motors (52) in response to the time being below a predetermined time period in any pulse to either motor (52).

2. A method as set forth in claim 1 including the step of restarting the pulses after each termination of energy.

3. A method as set forth in claim 1 including oscillating the energy in each pulse at a predetermined frequency.