WO1999050720A1

WO1999050720A1 - Dynamic system controller

Info

Publication number: WO1999050720A1
Application number: PCT/US1999/006623
Authority: WO
Inventors: David J. Hamo; Steve C. Southward; Matthew K. Ferguson
Original assignee: Lord Corporation
Priority date: 1998-04-01
Filing date: 1999-03-25
Publication date: 1999-10-07
Also published as: AU3206399A

Abstract

A dynamic system controller apparatus includes a controller in a portable housing having an external sensor input and an output for control of the dynamic system. The control operations of the controller include gain values which are adjustable responsive to manually configurable parameter select input such as a DIP (Dual In-line Package) switch. The controller may therefore be readily, manually configured to the dynamic system, such as a seat suspension system, with which it is to be utilized. For a seat suspension damper system, a different set of gain values may be provided for different model seats. The controller may, therefore, be readily installed into existing systems without requiring reprogramming and the associated greater equipment costs of reprogramming to adjust controller performance. The DIP switch is preferably located within the controller housing and set at the time of installation. A mode control input may also be provided with a plurality of states which are selectable by a user based on user preferences. Multi-rate processing is provided to allow the use of lower cost hardware in the dynamic system controller apparatus while maintaining system performance.

Description

DYNAMIC SYSTEM CONTROLLER

Field Of The Invention

This invention relates to controllers for dynamic systems such as damper systems or noise and vibration control systems. More particularly, this invention relates to controllers for closed loop systems having control output signals generated responsive to an input signal.

Background of the Invention

It is known to provide for control of dynamic systems through the use of a control output signal which is varied responsive to an input signal to control the behavior of the system to maintain a desired state. Two examples of such dynamic systems are controllable damper systems and active noise and vibration control systems.

Controllable damper systems have been proposed for a number of applications, including trucks, off-highway equipment, construction equipment, and automotive. Controllable dampers may provide continuous adjustment of the output force over a significant range, as opposed to passive systems which have unchangeable operating characteristics. Controllable fluid dampers, which are available in various types, are particularly advantageous because of the relatively fast response time. An example of such a system is U.S. Patent No. 5,277,281 to Carlson et al. which discloses a magnetorheological fluid damper. An electrophoretic fluid damper is disclosed in U.S. Patent No. 5,018,606 to Carlson. U.S. Patent No. 5,522,481 to Watanabe discloses an electrorheological fluid damper. These type dampers are controlled by changing the electric or magnetic field applied to a fluid whose apparent viscosity is responsive to the field.

One advantageous use for controllable dampers is in primary or secondary suspension systems, for example, suspension systems for vehicle seats or cabs. Isolating the seat or cab from the vehicle frame to protect the operator from vibrations transmitted through the vehicle can improve the operator's ability to control the vehicle and may reduce vibrations experienced by the operator. 2

An example of such a system is found in United States Patent No. 5,652,704 entitled "Controllable Seat Damper System and Control Method ThereforJ the disclosure of which is hereby incorporated by reference as if set forth in its entirety. This patent discloses systems using a controllable fluid damper such as a magnetorheological (MR) type, in combination with vehicle suspension systems. In such a system, for example, a seat suspension system, the system actively controls damping by sensing the seat position and the rate of change of the seat position and calculates an appropriate damping force based on a stored algorithm.

In the realm of active noise and vibration control, there are various implementation approaches including: active noise control, which uses an inverse phase sound wave to cancel the disturbing signal; active structural control, which vibrates a structural component at one or frequencies to cancel the input disturbance (noise and/or vibration); and active isolation control, where an actuator in a mount is reciprocated at the proper frequencies, phase and amplitude to cancel the input disturbance (which, again, may be a structural vibration or in the audible range, in which case it is experienced as noise).

Active vibration and sound control systems generally utilize a controller to control or minimize mechanical vibration or ambient noise levels at a defined location or locations. Generally, these active systems are responsive to at least one external input signal such as a feedforward reference signal and/or error signal as supplied by various types of sensors such as microphones, accelerometers, tachometers etc. Generally these systems strive to reduce to zero or at least minimize the residual sound and/or vibration.

An example of such an active noise/vibration control system is illustrated in FIG. 1 and further described in United States Patent Application No. 08/698,544 entitled "Active Noise and Vibration Control System" the disclosure of which is hereby incorporated herein by reference as if set forth in its entirety. As illustrated in FIG. 1, aircraft 10, shown in cross-section, includes fuselage 12 defining passenger compartment 13 connected by mounts 14, 14' to vibrational energy source/members (engines) 16, 16'. Active vibration control actuators 18, 18' or other actuator means for generating forces to control vibrational energy, as illustrated in FIG. 1, are mounted in mounts 14, 14', respectively. Sensors 20, 20' or other sensor means for 3 monitoring vibrational (or noise) energy, as illustrated in FIG. 1 may be positioned within passenger compartment 13 to detect noise and/or vibration to be controlled within passenger compartment 13. Also shown are feedforward reference sensors 15, 15', or other sensor means for monitoring vibrational (or noise) energy to be controlled mounted to the casings of engines 16, 16'. Alternatively, tachometer sensors could be used. Actuators 18, 18' and sensors 15, 15', 20, 20', are electrically connected to driver/controller 21. In an active vibrational energy control system, driver/controller 21 acts responsive to input from sensor 20 to drive actuators 18, 18' in a manner to reduce or eliminate noise and/or vibration generated by vibrational energy sources (engines) 16, 16'.

The performance of dynamic systems such as damper systems and active noise and vibration control systems is typically directly impacted by the controller used to control the system control outputs responsive to the sensor inputs. The performance of the controller is also dependent on and subject to variations in the dynamic systems being controlled and the preferences of the user of the systems which will affect the user's perceived performance of the system. The controllers are also subject to noise on the sensor inputs which may cause undesirable changes in the system control output. Accordingly, it is desirable to have a controller which may be adaptable to changes in the dynamic system it is connected to and the preferences of a user. It is also desirable to control noise on sensor input signals without adversely affecting system responsiveness. It is known in some areas of control to provide user input means such as a computer terminal including a keyboard to allow a user to adjust the control characteristics of the system. However, providing a controller adapted to meet all of these various objectives can result in excessive system cost for many applications. 4 Summary of the Invention

It is, therefore, an object of the present invention to provide an improved controller for controlling dynamic systems which includes adjustable gain values.

It is another object of the present invention to provide a dynamic system controller apparatus including signal conditioning for sensor inputs.

It is a further object of the present invention to provide a dynamic system controller apparatus which may be implemented utilizing low cost components and be readily adjusted to work with different dynamic systems and user preferences.

These and other objects are provided, according to the invention, by providing a controller in a portable housing having an external sensor input and an output for control of the dynamic system. The closed loop control operations of the controller include gain values which are adjustable responsive to a parameter select input such as a DIP (Dual In-line Package) switch. The controller may therefore be readily, manually configured to the dynamic system with which it is to be utilized. For example, a seat suspension damper system may have a different set of gain values for different model seats. The controller may, therefore, be readily installed into existing systems without requiring reprogramming and the associated greater equipment costs of reprogramming to adjust controller performance. The DIP switch is preferably located within the controller housing and may be set at the time of installation or at the factory. A mode control input may also be provided with a plurality of states which are selectable by a user. Multi-rate processing may be utilized to allow the use of lower cost hardware while maintaining system performance.

In particular, a dynamic system controller apparatus is provided according to a first aspect of the present invention. The controller apparatus is contained within a portable housing and includes a controller positioned in the housing. An external sensor input passes into the housing and is coupled to the controller. A means for selecting control parameters is also positioned in the housing and coupled to the controller. Finally, the controller is also coupled to a system control output. The controller is configured by firmware to provide a means including a plurality of gain values for adjusting the system control output responsive to the sensor input and a means for setting at least one of the plurality of gain values responsive to the parameter select means. The apparatus may further include an external mode input 5 coupled to the controller in which case the controller also includes a means for setting at least one of the plurality of gain values responsive to the mode input.

In a further aspect of the apparatus of the present invention, a memory is provided which is coupled to the controller. The memory provides a means for storing at least one limit value for the external sensor input. The controller further includes means for setting at least one of the plurality of gain values responsive to the limit value in the memory. In one embodiment of this aspect of the present invention, the memory is a programmable memory and the controller further includes a calibration means for setting the limit value responsive to the external sensor input. In addition, the calibration means may be responsive to the external mode input for initiating setting of the limit value. Finally, the controller may include means for testing the memory and providing an indication of status of the memory on the external mode input.

The apparatus of the present invention may also be provided with a voltage to current amplifier coupling the controller to the system control output in which case the output is a current regulated output. A position sensor may be provided as a part of the apparatus which is mounted on the housing and coupled to the external sensor input to provide the input signal.

In one embodiment of the apparatus of the present invention, the means for selecting control parameters is a manually reconfigurable parameter select switch. The switch may be a mechanical switch such as a DIP switch. The switch may, alternatively, be a receptacle configured to receive a resistor.

In a multi-rate processing aspect of the apparatus of the present invention, the apparatus further includes a filter means for filtering the external sensor input. The filter means may include a single-pole analog filter connected to the external sensor input and an analog to digital converter having an analog input coupled to the analog filter and having a digital output. In this embodiment, the controller further includes a digital filter means coupled to the digital output of the analog to digital converter for filtering a signal from the analog to digital converter. A zero-order hold means for capturing the output of the digital filter means at a first sample rate may also be provided. The digital filter means reads the digital output of the analog to digital converter at a second sample rate and the means for adjusting the system control 6 output includes means for reading the output of the zero-order hold means at a third sample rate. The first sample rate and the second sample rate are preferably the same sample rate and are higher than the third sample rate. In a particular embodiment for a motor vehicle seat suspension system, the third sample rate is 200 Hz and the first sample rate and the second sample rate are 1000 Hz. In this embodiment, the analog filter has a first breakpoint frequency which is less than about 100 Hz and preferably about 40 Hz and the digital filter means has a second breakpoint frequency lower than the first breakpoint frequency of less than about 50 Hz and preferably about 20 Hz.

In a further aspect of the present invention, a damper controller apparatus is provided. The apparatus includes a controller and a sensor input coupled to the controller. A parameter select circuit is coupled to the controller which includes a manually reconfigurable parameter select switch. A damper output is coupled to the controller as is a memory which includes a limit value for the external sensor input. The controller includes firmware providing a means including a plurality of gain values for adjusting the damper output responsive to the sensor input, means for setting at least one of the plurality of gain values responsive to the parameter select circuit, means for comparing a signal from the sensor input to the limit value and setting at least one of the plurality of gain values to a first value when the signal from the sensor input exceeds the limit value and a second value when the signal from sensor input does not exceed the limit value and a means for calibrating the limit value based on signals from the sensor input. The means for calibrating in one embodiment includes means for storing a value based on a first signal from the sensor input as a first limit value responsive to a first input signal from the mode input and for storing a value based on a second signal from the sensor input as a second limit value responsive to a second input signal from the mode input.

In a further aspect of the present invention a multi-rate processing dynamic system controller apparatus is provided. The apparatus includes a sensor input and an analog filter having an input node connected to the sensor input. An analog to digital converter is coupled to the analog filter. A digital filter means is coupled to the analog to digital converter for filtering a signal from the analog to digital converter. A system control output is also provided along with a means coupled to the digital filter 7 means for adjusting the system control output responsive to the output -of the digital filter means.

In a further aspect of the dynamic system controller apparatus of the present invention, a first circuit board and a second circuit board coupled to the first circuit board by a digital communication bus are provided. The analog filter, analog to digital converter, digital filter means and zero-order hold means are mounted on the first circuit board and the means for adjusting the system control output is mounted on the second circuit board. A first processor is mounted on the first circuit board and the digital filter means and zero order hold means are contained on the first processor. The first processor is preferably a fixed point processor and the means for adjusting the system control output is preferably a floating point processor. In one embodiment of this aspect of the present invention, the sensor input, analog filter, analog to digital filter means and zero-order hold define an input channel and the first circuit board includes a plurality of input channels to thereby support a plurality of input sensors rather than a single sensor. A plurality of the first circuit boards may be provided each of which is coupled to the second circuit board by the digital communication bus.

Accordingly, the present invention provides dynamic system controller apparatus which are readily configurable for a variety of systems with the capability to conform with variations in the system being controlled and the user's preferences. In addition, the apparatus of the present invention provide for multi-rate processing in a controller allowing the use of lower cost hardware without sacrificing system performance.

8 Brief Description of the Drawings

FIG. 1 is a schematic illustrating an active noise and vibration control system environment in an aircraft;

FIG. 2 is a schematic illustrating a cross-sectional side view of a seat suspension system including a dynamic system controller according to an embodiment of the present invention;

FIG. 3 is a block diagram of the embodiment of FIG. 2;

FIG. 4 is a block diagram of a dynamic system controller apparatus according to an embodiment of the present invention for use with a seat suspension system;

FIG. 5 is a flowchart illustrating calibration operations for an embodiment of a seat suspension system controller apparatus according to the present invention;

FIG. 6 is a block diagram of input sensor signal conditioning according to a multi-rate processing embodiment of the present invention;

FIG. 7 is a block diagram of output signal conditioning according to a multi- rate processing embodiment of the present invention; and

FIG. 8 is a block diagram of a dynamic system controller apparatus according to a further embodiment of the present invention suitable for use with an active noise and vibration control system.

9 Detailed Description of the Preferred Embodiments

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

A controllable seat suspension system including a dynamic system controller apparatus (more particularly a damper controller) according to the present invention is schematically illustrated in FIG. 2. The illustrated seat and suspension system are similar to those disclosed in U.S. Patent No. 5,562,704. Although the invention is described below primarily in terms of a specific seat suspension system, it will be appreciated that the invention may be used in connection with any dynamic system, and the following description is meant to be illustrative rather than limiting.

The controllable suspension system includes a suspended body 20, which can be a seat or a vehicle cab, for example, mounted to a frame 21 which accordingly can be a floor of a cab or the structural frame of a vehicle. For purposes of the illustration and description, the frame 21 is a part of a vehicle (a truck, an off -road vehicle, or construction apparatus, for example), and the body is a seat 20 for an operator (user). A suspension system 30 isolates the body 20 from vibrations of the frame 21. The suspension system 30 includes a spring 32 and a support 34. The spring 32 in the illustrated embodiment is an air spring, which can be adjusted by use of an air source and valve (not illustrated). The support 34 is illustrated as a scissors mount, but other types of support devices which allow vertical movement and restrain horizontal movement can be used as convenient.

A controllable damper system 40 is connected in parallel relationship with the spring 32 and support 34 to isolate the body 20 from vibrations of the frame 21. The controllable damper system 40 includes a damper 42 operably mounted to a bracket which mounts to the frame 21 and the body 20. Alternatively, the damper 42 could be mounted between the frame and the scissors mount or between the various scissors 10 components. The damper 42 may be a controllable fluid damper as disclosed by U.S. Patent No. 5,277,281, U.S. Patent No. 5,018,606, or U.S. Patent No. 5,522,481.

A position sensor 50 is mounted at the axis of the scissors support 34 to detect the position of the seat 20. Alternatively, the position sensor could be mounted between any two relatively moving suspension components, as is shown by sensor 50' at an optional location between the frame 21 and a leg of the scissors. The displacement of the seat can be obtained by comparison of position data taken over time. The position sensor 50 may conveniently be a variable resistor which produces a range of voltages corresponding to a range of seat positions, such as a potentiometer. A Hall effect sensor could also be used.

The damper system 40 includes a dynamic system controller apparatus 44, which is shown mounted to the bottom of the seat 20 for convenient access by the operator, but could be mounted on other suitable structures. An optional seat leveling switch 46 coupled to the controller apparatus 44 allows manual selection of the vertical position of the seat. The controller apparatus 44 is shown as including a portable housing 45 which may be mounted at various locations. For example, in one embodiment of the present invention, position sensor 50 is mounted on housing 45 and controller apparatus 44 is positioned to allow position sensor 50 to detect the position of seat 20.

As will be appreciated, the seat 20 can move through a range of height positions, from a bottom position to an upper position as permitted by the scissors support 34 or the damper stroke. The controller apparatus 44 in conjunction with the leveling switch 46 may be used to change the pressure in the air spring 32 to adjust the seat height position.

FIG. 3 is a block diagram illustrating connections to controller apparatus 44. An automotive battery 49 (preferably 12 or 24 volts) powers the controller apparatus 44. The controller apparatus 44 receives information from various sensors and other components, generally indicated by arrows pointing toward the microprocessor, and commands other components to act, generally indicated by arrows pointing away from the controller apparatus 44. Thus, a signal from the seat leveling switch 46 to change 11 the position of the seat is received and processed by the controller apparatus 44. and a signal is sent to the air spring valve 38 to change the air spring pressure accordingly.

As described in U.S. Patent No. 5,652,704, the controller apparatus 44 receives data relating to the actual position of the seat, among other data, calculates the rate of change of position, and adjusts the damping level in the controllable damper 42. The damping level in the illustrated embodiment is a function of the actual position of the seat, the rate of displacement of seat, and the direction of the displacement.

Referring now to FIG. 4, a dynamic system controller apparatus 44 according to an embodiment of the present invention will now be further described. The seat level control feature of FIG. 3 is not present in the embodiment of FIG. 4. Controller apparatus 44 is contained within portable housing 45. Operations of controller apparatus 44 are controlled by microprocessor/controller 51 which is positioned within housing 45. An external sensor input 52 is coupled to controller 51 through input conditioning circuit 54. As described previously, sensor input 52 may be an analog voltage input from position sensor 50. Controller 51 is also coupled to external ride mode input 56. Ride mode input 56 may be provided by a ride mode switch (not shown) which may have a plurality of positions to allow a user to manually select control parameters to adjust the controlled ride in accordance with the user's wishes. In the case of controllable seat suspension systems, three positions such as "softJ "medium" and "firm" have been found to be adequate without overwhelming the user with too many choices. Different labels may be chosen for the mode select positions depending upon the particular usage. The values for each of these mode settings are preferably factory set and known to controller 51.

Mode input 56 from a ride mode switch permits the feel of the seat suspension system to be adjusted to the preferences of the user. These choices may be use related or simply tied to the ride feel preference of the user. The manual adjustment from the switch input to mode input 56 is utilized to select a different set of gain values which are chosen for each application and are accessible to controller 51. While the selectable parameters are generally referred to herein as "gain values/' it is to be understood that term as used herein is intended to encompass any parameter affecting 12 the transfer function between the sensor input 52 and control output 70 such as filter frequency and null band limits.

Also shown in FIG. 4 is power input 58 which provides electrical power for controller apparatus 44. The power input from line 58 is conditioned by power regulator 60 to be suitably regulated for operating the electrical components of controller apparatus 44. While the output of power regulator 60, as shown in FIG. 4, is only connected to controller 51, it is to be understood that power regulator 60 may provide a regulated voltage power supply to all of the electrical components contained within controller apparatus 44.

In addition to power regulator 60, voltage monitor 62 is also illustrated in the embodiment of FIG.4. Voltage monitor 62 monitors the output voltage of regulator 60 and provides an indicator of a fault condition if the output voltage goes outside of an acceptable band. The fault indication output from voltage monitor 62 may be utilized as an input to controller 51 triggering a system reset when the supply voltage from power regulator 60 has exceeded the operating limits recommended for controller 51.

Controller apparatus 44 further includes parameter select circuit 64 contained within housing 45. Parameter select circuit 64 is coupled to controller 51 and provides means for selecting control parameters for use by controller 51. As illustrated in FIG. 4, parameter select circuit 64 includes switch 66 which provides a manually reconfigurable parameter select switch. Switch 66 may be a mechanical switch such as a "DIP" switch allowing manual toggling by an operator of a plurality of lines between the zero and one state. Alternatively, switch 66 may be a receptable configured to receive one or more resistors. The insertable resistors would typically couple the parameter select line to a high state voltage such as plus 5 volts providing for a zero state on the select when no resistor is inserted and a one state when a resistor is inserted.

Controller 51 includes output signal 68 which couples controller 51 to system control output 70 (a current regulated damper output in the illustrated embodiment) through output conditioning 72. 13

Controller 51 includes firmware coding executable by controller 51 to generate output 68. Accordingly, controller 51 provides a means including a plurality of gain values for adjusting system control output 70 responsive to input 52. Controller 51 further includes means for setting at least one of the plurality of gain values responsive to a parameter select signal from parameter select circuit 64. The parameter select signals from parameter select circuit 64 to controller 51 will typically be a plurality of binary inputs. Accordingly, the number of parameter sets available for selection will depend on the number of input lines connecting parameter select circuit 64 to controller 51. For example, two input lines would provide four possible parameter set selections, three input lines would provide eight possible parameter set selections and so on (related by two raised to the power of the number of inputs). Each of the parameter set select inputs may correspond to a different manufacturer's seat or a different model of seat from a different manufacturer in the case of a seat suspension system application of the present invention.

For the embodiment of FIG. 4, controller 51 also includes a means for setting at least one of the plurality of gain values responsive to mode input 56. Various possible mode inputs have been described previously. In the embodiment of FIG. 4, the number of available mode input setting selections corresponds to the number of input lines as previously described for the parameter select inputs.

For the embodiment of FIG. 4, where gain values for controller 51 may vary based upon the parameters selected and the mode input, the gain values are preferably stored in multi-dimensional look up tables. For example, each of the gain values could be stored in a two-dimensional array containing a value for each combination of parameter select and mode select inputs. Alternatively, a three-dimensional array may be provided with the mode and parameter selections identifying a vector of gain values for use by the means for adjusting system control output 70 responsive to sensor input 52 where more than one gain value is selectable.

In various types of dynamic systems, including seat suspension systems which have mechanical travel limits as constraints on the behavior of the system being controlled, it is desirable to establish limit values affecting gain values as travel limits are approached. In the case of a vehicle seat suspension for an application such as that 14 illustrated in FIG.2, the physical limits of the system are the bottom and top limits of vertical travel provided by the mechanics of the seat. Limit values for control of the seat suspension system are, therefore, selected at an offset from those physical limits to provide, typically, stiffer dampening of the system as the physical travel limits are approached. This aids the system in avoiding sudden or rapid contact of the seat 20 at its physical travel limits.

As is clear from the description of parameter select circuit 64, controller apparatus 44 is configured to work with a variety of different systems which makes it desirable for controller apparatus 44 to have the ability to determine physical travel limits and establish end stop limit values at which increased damping may be used to avoid sudden collision with a maximum or minimum position. Calibration may also be desirable to accommodate variations during installation of the positioning of the input sensors and the like may vary.

Accordingly, controller apparatus 44 as illustrated in the embodiment of FIG. 4 also includes memory 74 coupled to controller 51. While illustrated as a separate device, memory 74 may be internal to controller 51. Memory 74 includes end stop limit values for sensor input 52. Controller 51 further includes means for setting at least one of the plurality of gain values responsive to the limit values stored in memory 74. In addition, controller 51 includes calibration means for setting the limit values stored in memory 74 responsive to inputs read from sensor input 52. One method for calibration to establish the limit values to be stored in memory 74 is disclosed in commonly owned U.S. Patent application No. 08/874,364 entitled "Method for Auto-Calibration of a Controllable Damper Suspension System," the disclosure of which is incorporated herein by reference as if set forth in its entirety. For the embodiment illustrated in FIG. 4, a simplified calibration method is provided responsive to signals from mode input 56 which initiate setting of the limit values.

Referring now to FIG. 5, operations for calibration of limit values will be described for an embodiment of the present invention. At block 80, controller 51 reads mode input 56 to determine if the plurality of input pins defining mode input 56 have been shorted. In practice, this shorting may be accomplished by the system installer during installation by utilizing a shorting clip to short out the inputs. If a 15 short is not detected at block 80, controller 51 assumes that calibration has not been initiated and resumes normal operation. In a preferred embodiment of the present invention, controller 51 checks for a short condition on mode input 56 on each power up of controller apparatus 44. If a short is detected at block 80, controller 51 reads sensor input 52 at block 82 and treats the read value as a lower travel limit reading from position sensor 50 or other sensor input means. Accordingly, the operator performing the calibration should move the seat under control to its lower limit position before inserting the shorting clip and powering up controller apparatus 44.

At block 84, controller 51 calculates a lower end stop limit value which is typically an offset of some limited distance from the lower travel limit reading. This calculated lower end limit value is stored in memory 74 by controller 51 at block 84. Controller 51 continues operations in the calibration mode at block 86 by monitoring mode input 56 to determine if the mode input pins have had the short removed. Once the short is removed, controller 51 reads sensor input 52 as the upper travel limit value at block 88.

In a manner similar to that described for the lower end stop limit value determination, an upper end stop limit value is calculated at block 90 representing some offset distance before the upper travel limit is reached. The calculated upper limit value is stored in memory 74 at block 90. The calibration procedure is then completed and controller 51 returns to normal operations.

Calibration operations have been described with reference to FIG. 5 for an embodiment in which the lower travel limit is read on insertion of the short and the upper travel limit is read later on removal of the short. However, it is to be understood that the lower and upper position reading in the sequence could be reversed while still practicing the present invention.

As described, the end stop limit values represent position ranges near the extreme seat positions. The end stops are used as triggers to increase the damping to prevent the seat from colliding with the suspension structure at the end of the range of motion or bottoming out of the damper itself. The end stop limit values are preferably calculated as a percentage of the complete range of motion, and for a truck seat, for example, may be set at 30% for the upper limit and 20% for the lower limit. In 16 embodiments wherein seat leveling capability is provided, the end stops may also be used to limit the range of leveling available to the user for positioning the seat. Optionally, the end stop limit values may be predetermined values. The end stop limit values may also be calculated dynamically by controller 51 based on the travel limits, position and velocity (as calculated, for example, based on a derivative of a position sensor input) rather then being calculated as described above and stored. Providing end stop limit values that are a function of velocity allows the end stop limits to change based on how fast the travel limit is being approached thereby allowing an end stop limit value very close to the travel limit for low velocities (and proportionately larger for higher velocities). For this embodiment of the present invention, the limit values stored in memory 74 would, preferably be the travel limits as read from the sensor input.

Signal conditioning operations and associated circuitry will now be described with respect to conditioning of the sensor input signal 52 with reference to the block diagram of FIG. 6. In the embodiment of input signal conditioning of FIG. 6, a portion of the filtering operations are preferably implemented by code within controller 51 as illustrated by the dotted line box in FIG. 6. The remaining blocks in FIG. 6 represent an embodiment of input conditioning circuit 54 from FIG. 4.

As shown in FIG. 6, sensor input 52 is first processed through analog filter 100. For a damper controller system such as the seat suspension systems described herein, analog filter 100 may be provided as a simple, low cost, single-pole analog filter connected to sensor input 52. A commonly used RC filter circuit is suitable for use as analog filter 100 in such an application. As will be described later herein, a more complicated analog filter providing a steeper fall off after the break frequency, such as a second order filter provided with real poles, may be more suitable in active noise and vibration control applications.

For a damper control system embodiment of the present invention, analog filter 100 preferably has a breakpoint frequency of less than about 100Hz and, more preferably, for a typical truck seat system, will have a breakpoint frequency of about 40 Hz. 17

The output of analog filter 100 is sampled by analog to digital .converter 102 to provide a digital representation of the analog filtered sensor input 52. Analog to digital converter 102 has an analog input shown coming from analog filter 100 and a digital output shown as an arrow to digital filter 104 of controller 51. Digital filter 104 samples digital output values from analog to digital converter 102 and provides filtered digital output values to zero order hold means 106. Digital filter 104 provides a means coupled to the digital output of analog to digital converter 102 for filtering a signal from analog to digital converter 102. Zero order hold means 106 has an output which is, in turn, provided to the means for adjusting the system control output responsive to sensor input 52 of controller 51.

Zero order hold means 106 captures the output of digital filter 104 at a first sample rate. Digital filter 106 reads the digital output of analog to digital converter 102 at a second sample rate. The means for adjusting the system control output responsive to a sensor output of controller 51, in turn, reads the output of zero order hold means 106 at a third sample rate. The first sample rate and second sample rate may be the same sample rate. Each of these rates is provided as higher than the third sample rate to allow for a multi-rate processing as will now be described further.

The circuit of FIG. 6 provides for an economical design of controller apparatus 44 by employing multi-rate processing. Utilizing multi-rate processing for a dynamic system controller allows controller 51 to run control operations for updating system control output 70 at a fixed base sample rate while the input sampling process runs at an integer multiple of this base rate. As a result, a lower-cost, less capable processor may be used for controller 51 without sacrificing dynamic system performance. Furthermore, by implementing digital filter 104 in controller 51 for additional signal conditioning of sensor input 52, the requirements for analog filter 100 may be effectively reduced. This allows simpler and less costly components to be used for analog filter 100. Accordingly, utilizing the embodiment of FIG. 6 allows the use of a single pole analog filter for applications which would otherwise require a more complex filter to provide a greater fall off rate after the frequency breakpoint to accomplish both anti-aliasing and signal noise reduction. 18

While digital filter 104 and zero order hold 106 in the embodiment illustrated in FIG. 6 are both implemented on controller 51, it is to be understood that they may also be provided by discrete digital circuitry coupled to controller 51. However, incorporating these elements in controller 51 provides for reduced cost and increased simplicity for controller apparatus 44. In multi-rate processing applications in the field of digital signal processing, analog filter 100 is sometimes referred to as antialiasing filter and digital filter 104 is sometimes referred to as a decimation filter. The digital filter 104 in conjunction with zero order hold 106 defines a decimator.

For the seat suspension control embodiment of the present invention discussed herein, digital filter 104 preferably is a low-pass filter having a a breakpoint frequency less than about 50 Hz and more preferably has a breakpoint frequency about 20 Hz. The processing rates for the multi-processing embodiment of FIG. 5 may be successfully implemented with a low cost controller by providing a 200 Hz base sampling rate and a 1000 Hz sampling rate on the input signal end for digital filter 104 and analog to digital converter 102. In this embodiment, zero order hold 106 may be clock operated at either the higher or lower sampling rate, preferably at the higher sampling clock rate (i.e., input at higher rate but outputting only every fifth filtered output value from digital filter 104).

While the operations of the multi-rate processing apparatus of FIG. 6 have been described with respect to particular values for breakpoint frequencies and processing rates based upon a vehicle seat damper control system, it is to be understood that the benefits of the present invention may be utilized for other types of dynamic systems using different filter design values and processing rates. While optimized values for a vehicle seat suspension system have been discovered by the present inventors, that those of ordinary skill in the art, in light of this disclosure, are able to select appropriate breakpoint frequencies and filter designs meeting the processing speed, anti-aliasing and noise control requirements of various dynamic systems.

Multi-rate processing may also be beneficially applied in a dynamic system controller apparatus 44 according to the present invention on the output signal side as illustrated by the embodiment of FIG. 7. A control signal to system control output 70 19 is processed first through digital filter 110 and then passed to circuit 112. Depending upon the application chosen, circuit 112 may either be a digital to analog converter or a pulse width modulation (PWM) circuit. Furthermore, while not shown in FIG. 7, the output voltage signal from circuit 112 may be provided to a voltage to current regulated amplifier to provide system control output 70 as a current rather than a voltage regulated output. In any event, an analog reconstruction filter 114 may be provided for multi-rate processing of the output side of the system. For the embodiment of a vehicle seat suspension system described herein, digital inteφolation filter 110 may be provided as a single-pole digital filter having a 20 Hz frequency breakpoint. In such an embodiment, analog filter 114 may be provided as a single- pole analog filter having a 100 Hz frequency breakpoint where circuit 112 is a PWM circuit.

As noted above, the multi-rate processing technique provided through the circuitry of FIG. 6 and FIG. 7 allows a very low-order design of the analog filters. The output of the analog anti-aliasing filter 100 is sampled at a "high" rate. The sampled signal is then passed through a digital decimation filter 104 to further low- pass filter the signal. An increase in the effective resolution is possible if the 8-bit analog to digital converter 102 samples are scaled up appropriately in decimation filter 104. The output of the digital decimation filter 104 is sampled at a lower rate, as indicated by the zero order hold 106 in FIG. 6. In other words, for the illustrated embodiment, only every nth sample output from filter 104 is utilized which, for the particular embodiment identified above, would be every fifth sample. The means for adjusting the system control output in controller 51 produces updated outputs for control output 70 at the sub-sampled rate. The digital inteφolation filter 110 may, therefore, be utilized to allow control output 70 to be sampled at a higher rate. Inteφolation filter 110 is functionally equivalent to decimation filter 104 and plays a similar role for output signal 70. If the optional inteφolation filter 110 is not used, the output signal passed to digital to analog converter/PWM 112 may be held constant for all consecutive n samples.

A further embodiment of a dynamic system controller apparatus according to the present invention will now be described with reference to FIG. 8. The 20 embodiment of FIG. 8 is directed to an active noise and vibration control dynamic system controller apparatus. As will be apparent from the discussion of FIG. 8, the demands on such a system are typically more rigorous than those for a seat suspension damper control system. For the embodiment of FIG. 8, the electronics of controller apparatus 44 are provided on two separate circuit boards 120, 130, which are connected by a high speed digital communication bus 140. A plurality of sensor inputs 52 and control outputs 70 are illustrated in FIG. 8. While only one input channel and one output channel will be described herein, it is to be understood that operations are performed similarly for each input channel and output channel. Additional channels allow the use of additional sensors and output control signals in a dynamic system control environment.

Input 52 is first amplified by amplifier 142 on first circuit board 120. The amplified signal is then provided to analog filter 144 which, in the illustrated embodiment, is a second order analog low-pass filter provided with real poles having a 465 Hz breakpoint. The output of analog filter 144 is provided to analog to digital converter 146. The digital output from analog to digital converter 146 is, in turn, provided to digital decimation filter 148. Decimation filter 148, in the illustrated embodiment, is a sixth order low-pass filter with three Bi-Quadratic sections (Bi- Quad) having a 400 Hz breakpoint frequency and an 8,000 Hz sample rate. The output from decimation filter 148 is sampled at 1 ,000 Hz as illustrated by circuit 150. The sampled input signal is then passed over communication bus 140 to the second circuit board 130 which contains floating point processor 152 operating at a 1 ,000 Hz sample rate.

It is to be understood that analog anti-aliasing filter 144 corresponds to filter 100 of FIG. 6. Converter 146 corresponds to converter 102 of FIG. 6, decimation filter 148 corresponds to digital filter 104 of FIG. 6 and sampler circuit 150 corresponds to zero order hold 106 of FIG. 6.

On the output side, the output from control processor 152 is sampled at block 154 to a 8,000 Hz rate in accordance with known inteφolation filter requirements from digital filter processing. The sampled output is then passed through inteφolation filter 156. Inteφolation filter 156, in the illustrated embodiment, is a 21 sixth order low-pass filter with three Bi-Quads having a 400 Hz breakpoint frequency and an 8,000 Hz sample rate. The output of inteφolation filter 156 is then passed to digital to analog converter 158 and from there to analog reconstruction filter 160 and finally to an amplifier circuit 162 before being output from controller apparatus 44 to an output device in the dynamic system. As illustrated in FIG. 8, by box 164, decimation filters 148, sampler circuits 150, sampler circuits 154 and inteφolation filters 156 are implemented on a fixed point digital signal processor.

By providing separate boards 120 and 130 with processors on each board, the embodiment of FIG. 8 provides for the support of multiple input/output modules 120 by a single digital control module 130. For the illustrated embodiment of FIG. 8, each input/output module board 120 supports 24 input channels and 16 output channels. A single digital control module board 130 may support a plurality of input/output module cards 120 off of a common communication bus 140. This approach provides for flexibility for system design and expandability.

The embodiment of FIG. 8 also provides for a reduced board area over prior art systems thereby reducing the weight of controller apparatus 44. The design of FIG. 8 further provides reduced component count, thereby increasing the overall reliability of the control system and reducing system cost. Variability due to component tolerances, temperature variation and other environmental factors is reduced between input and output paths by providing half of the filtering digitally and the other half with analog filters which are relatively insensitive to component tolerances and temperature variations.

As shown in the embodiment of FIG. 8, analog filters 144 and 160 are each provided as higher-order filters than was disclosed with respect to the damper system application of FIGS. 6 and 7. However, filter 144, like filter 100, is a relatively low- order filter for the particular dynamic system to which it is applied. Accordingly, the embodiment of FIG. 8 provides benefits in the active noise and vibration control dynamic environment comparable to those for the seat damper control system of FIGS. 6 and 7.

As will be appreciated by those of skill in the art, the above described aspects of the present invention in FIGS. 3, 4, 6, 7 and 8 may be provided by hardware, 22 software, or a combination of the above. While various components of the apparatus of the present invention have been illustrated in part as discrete elements in the figures, they may, in practice, be implemented by a microcontroller including input and output ports and running software code, by custom or hybrid chips, by discrete components or by a combination of the above. For example, memory 74 may be implemented as a discrete device, a segment of existing memory or contained within controller 51. Similarly, digital to analog converter/PWM 112 may be a discrete device or contained within controller 51.

The present invention has been described above with respect to FIG. 5 with reference to a flowchart illustrating operations for a calibration aspect of the present invention. It will be understood that each block of the flowchart illustration, and combinations of blocks in the flowchart illustration, can be implemented by computer program instructions. These program instructions may be provided to a processor to produce a machine, such that the instructions which execute on the processor create means for implementing the functions specified in the flowchart block or blocks. The computer program instructions may be executed by a processor to cause a series of operational steps to be performed by the processor to produce a computer implemented process such that the instructions which execute on the processor provide steps for implementing the functions specified in the flowchart block or blocks.

In the drawings and specification, there have been disclosed typical preferred embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for puφoses of limitation, the scope of the invention being set forth in the following claims.

Claims

23ClaimsThat Which Is Claimed Is:

1. A dynamic system controller apparatus comprising: a portable housing; a controller positioned in said housing; an external sensor input coupled to said controller; means for selecting control parameters positioned in said housing and coupled to said controller; a system control output coupled to said controller; and wherein said controller comprises: means including a plurality of gain values for adjusting said system control output responsive to said sensor input; and means for setting at least one of said plurality of gain values responsive to said means for selecting control parameters.

2. The apparatus of Claim 1 further comprising: an external mode input coupled to said controller; and wherein said controller further comprises means for setting at least one of said plurality of gain values responsive to said mode input.

3. The apparatus of Claim 2 further comprising: a memory coupled to said controller, said memory including a limit value for said external sensor input; and wherein said controller further comprises means for setting at least one of said plurality of gain values responsive to said limit value in said memory.

4. The apparatus of Claim 3 wherein said memory is a programmable memory and wherein said controller further comprises calibration means for setting said limit value responsive to said external sensor input. 24

5. The apparatus of Claim 4 wherein said calibration means for setting said limit value is responsive to said external mode input for initiating setting of said limit value.

6. The apparatus of Claim 3 further comprising means for testing said memory and providing an indication of status of said memory on said external mode input.

7. The apparatus of Claim 1 further comprising a voltage to current amplifier coupling said controller to said system control output and wherein said system control output is a current regulated output.

8. The apparatus of Claim 1 further comprising a position sensor mounted on said housing and coupled to said external sensor input.

9. The apparatus of Claim 1 wherein said means for selecting control parameters is a manually reconfigurable parameter select switch.

10. The apparatus of Claim 9 wherein said parameter select switch switch is a dual inline package switch.

11. The apparatus of Claim 9 wherein said parameter select switch is a receptacle configured to receive a resistor.

12. The apparatus of Claim 1 further comprising filter means for filtering said external sensor input, said filter means coupling said external sensor input to said controller. 25

13. The apparatus of Claim 12 wherein said filter means comprises: a single-pole analog filter connected to said external sensor input; an analog to digital converter having an analog input coupled to said analog filter and having a digital output; and wherein said controller further comprises a digital filter means coupled to said digital output of said analog to digital converter for filtering a signal from said analog to digital converter, said digital filter means having an output.

14. The apparatus of Claim 13 wherein said controller further comprises: hold means for capturing said output of said digital filter means at a first sample rate, said hold means having an output; and wherein said digital filter means reads said digital output of said analog to digital converter at a second sample rate; wherein said means for adjusting said system control output includes means for reading said output of said hold means at a third sample rate; and wherein said analog filter has a first breakpoint frequency and said digital filter means has a second breakpoint frequency lower than said first breakpoint frequency.

15. The apparatus of Claim 14 wherein said first sample rate and said second sample rate are the same sample rate and are higher than said third sample rate.

16. The apparatus of Claim 15 wherein said first sample rate and said second sample rate are an integer multiple of said third sample rate, said integer multiple being between four and ten.

17. The apparatus of Claim 15 wherein said system control output is a damper control output and wherein said first breakpoint frequency is less than about 100 Hz and said second breakpoint frequency is less than about 50 Hz. 26

18. The apparatus of Claim 17 wherein said first breakpoint frequency is about 40 Hz and wherein said second breakpoint frequency is about 20 Hz.

19. A damper controller apparatus comprising: a controller; a sensor input coupled to said controller; a parameter select circuit coupled to said controller, said parameter select circuit including a manually reconfigurable parameter select switch; a damper output coupled to said controller; a memory coupled to said controller, said memory storing a limit value; and wherein said controller comprises: means including a plurality of gain values for adjusting said damper output responsive to said sensor input; means for setting at least one of said plurality of gain values responsive to said parameter select circuit; means for comparing a signal from said sensor input to said limit value in said memory and setting at least one of said plurality of gain values to a first value when said signal from said sensor input exceeds said limit value and a second value when said signal from said sensor input does not exceed said limit value; and means for calibrating said limit value based on signals from said sensor input.

20. The apparatus of Claim 19 further comprising a mode input coupled to said controller; and wherein said means for calibrating comprises means for initiating calibration responsive to a signal from said mode input.

21. The apparatus of Claim 20 wherein said means for calibrating comprises: means for storing a value based on a first signal from said sensor input as a first limit value responsive to a first input signal from said mode input and for storing 27 a value based on a second signal from said sensor input as a second limit value responsive to a second input signal from said mode input.

22. A dynamic system controller apparatus comprising: a sensor input; an analog filter having an input node connected to said sensor input and an output node; an analog to digital converter having an analog input coupled to said output node of said analog filter and having a digital output; digital filter means coupled to said digital output of said analog to digital converter for filtering a signal from said analog to digital converter, said digital filter means having an output; hold means for sampling the output of said digital filter means; a system control output; and means coupled to said output of said digital filter means for adjusting said system control output responsive to said output of said digital filter means.

23. The apparatus of Claim 22 further comprising: wherein said hold means is positioned between said digital filter means and said means for adjusting said system control output for capturing said output of said digital filter means at a first sample rate, said hold means having an output; and wherein said digital filter means reads said digital output of said analog to digital converter at a second sample rate; and wherein said means for adjusting said system control output includes means for reading said output of said hold means at a third sample rate.

24. The apparatus of Claim 23 wherein said first sample rate and said second sample rate are the same sample rate and are higher than said third sample rate. 28

25. The apparatus of Claim 24 wherein said first sample rate and said second sample rate are an integer multiple of said third sample rate, said integer multiple being between four and ten.

26. The apparatus of Claim 24 wherein said system control output is a damper control output and wherein said analog filter is a single-pole filter said first breakpoint frequency is less than about 100 Hz and said second breakpoint frequency is less than about 50 Hz.

27. The apparatus of Claim 23 wherein said analog filter has a first breakpoint frequency and said digital filter means has a second breakpoint frequency lower than said first breakpoint frequency

28. The apparatus of Claim 27 wherein said first breakpoint frequency is about 40 Hz and wherein said second breakpoint frequency is about 20 Hz.

29. The apparatus of Claim 24 further comprising a first circuit board and a second circuit board coupled to said first circuit board by a digital communication bus and wherein said analog filter, said analog to digital converter, said digital filter means and said hold means are mounted on said first circuit board and said means for adjusting said system control output is mounted on said second circuit board.

30. The apparatus of Claim 29 further comprising a first processor mounted on said first circuit board and wherein said digital filter means and said hold means are contained on said first processor.

31. The apparatus of Claim 30 wherein said first processor is a fixed point processor and said means for adjusting said system control output is a floating point processor. 29

32. The apparatus of Claim 29 wherein said sensor input, said analog filter, said analog to digital filter means and said hold means define an input channel and wherein said first circuit board includes a plurality of input channels.

33. The apparatus of Claim 32 further comprising a plurality of said first circuit boards each of which is coupled to said second circuit board by said digital communication bus.