WO2024070205A1

WO2024070205A1 - Cylinder device

Info

Publication number: WO2024070205A1
Application number: PCT/JP2023/028211
Authority: WO
Inventors: 央道菅原; 大和久保
Original assignee: カヤバ株式会社
Priority date: 2022-09-27
Filing date: 2023-08-02
Publication date: 2024-04-04
Also published as: JP2024047992A; JP7431915B1

Abstract

This cylinder device (A) comprises: a cylinder (2); a piston (3) that partitions the inside of the cylinder (2) into two working chambers (R1, R2); a first flow path (4) and a second flow path (5) that connect the working chambers (R1, R2) in parallel; a first variable throttle valve (6) provided in the first flow path (4); a hydraulic cylinder (1) having a second variable throttle valve (7) provided in series in the second flow path (5) and a bidirectional discharge type pump (9) driven by a motor (8); and a controller (11) that controls the first variable throttle valve (6), the second variable throttle valve (7), and the motor (8). The controller (11) determines a target aperture coefficient of the second variable throttle valve (7) at which the operating point of the motor (8) is placed on a straight line of maximum regeneration efficiency on the basis of the rotation speed of the motor (8) and the thrust of the hydraulic cylinder (1), and the controller controls the second variable throttle valve (7).

Description

Cylinder Unit

The present invention relates to a cylinder device.

A conventional cylinder device is, for example, as disclosed in JP2009-196597A, applied to active suspensions interposed between the body and axle of a vehicle, and specifically comprises a cylinder, a piston that is movably inserted into the cylinder to divide the inside of the cylinder into two working chambers, a rod connected to the piston, a first flow path and a second flow path that connect the two working chambers in parallel, a first variable throttle valve provided in the first flow path, a second variable throttle valve and a bidirectional discharge pump provided in series in the second flow path, a hydraulic cylinder having a motor that drives the pump, and a control device that controls the first variable throttle valve, the second variable throttle valve, and the motor.

When a conventional cylinder device is used as an active suspension, the cylinder is connected to one of the vehicle body and the axle, and the rod is connected to the other of the vehicle body and the axle. The pump is driven by a motor to generate thrust, thereby suppressing vibration of the vehicle body.

Furthermore, in conventional cylinder devices, when the hydraulic cylinder is forcibly extended or retracted by an external force, the pump is rotated by the hydraulic oil flowing through the second flow path, and the motor is used in the braking range to generate electricity and generate regenerative power. When the motor is used in the braking range in this way, the torque generated by the motor causes the pump to provide resistance to the flow of hydraulic oil. As a result, the hydraulic cylinder generates thrust that prevents the hydraulic cylinder from being extended or retracted by external forces.

JP2009-196597A

In conventional cylinder devices, the amount of hydraulic oil passing through the pump and the torque borne by the motor can be adjusted by adjusting the throttling coefficient of the first variable throttle valve and the throttling coefficient of the second variable throttle valve. Note that the throttling coefficient is the flow rate per unit time divided by the pressure, and a smaller throttling coefficient means greater resistance in the variable throttle valve.

When the motor is in a braking state, on a graph with motor torque on the vertical axis and motor rotation speed on the horizontal axis, the regenerative efficiency will be maximized if the intersection of the torque output by the motor and the motor rotation speed (motor operating point) is on a line (maximum regenerative efficiency line) that passes through the origin and has a slope half that of the line tangent to the short-circuit curve that shows the relationship between torque and rotation speed when the motor is short-circuited.

Therefore, in conventional cylinder devices, when the motor is in a braking state, the throttling coefficient of the first variable throttle valve and the throttling coefficient of the second variable throttle valve are adjusted so that the intersection of the torque output by the motor and the motor's rotational speed is located on the line that maximizes regenerative efficiency.

However, conventional cylinder devices do not specifically disclose what conditions the motor must be in to move the operating point of the motor onto the line of maximum regenerative efficiency, nor does it disclose how to control the first and second variable throttle valves to position the operating point of the motor on the line of maximum regenerative efficiency.

The present invention aims to provide a cylinder device that can actually maximize regenerative power by determining the conditions under which the operating point of the motor can be moved onto the straight line of maximum regenerative efficiency.

In order to achieve the above object, the cylinder device in the problem-solving means of the present invention comprises a hydraulic cylinder having a cylinder, a piston that is movably inserted into the cylinder and divides the inside of the cylinder into two working chambers, first and second flow paths that are parallel to each other and communicate the working chambers, a first variable throttle valve provided in the first flow path, a second variable throttle valve provided in series in the second flow path, and a bidirectional discharge pump driven by a motor, and a controller that controls the first variable throttle valve, the second variable throttle valve, and the motor, and when the operating point of the motor is located in a region of greater torque than the maximum regenerative efficiency line in the second quadrant or when the operating point of the motor is located in a region of less torque than the maximum regenerative efficiency line in the fourth quadrant in a rotational speed-torque coordinate system in which the operating state of the motor is in a braking state when the operating point of the motor is in the second and fourth quadrants, the controller calculates a target throttle coefficient of the second variable throttle valve that places the operating point of the motor on the maximum regenerative efficiency line based on the rotational speed and thrust generated by the hydraulic cylinder, and controls the second variable throttle valve. With this cylinder device configured, when the motor is in a braking state, enabling power regeneration, and the operating point of the motor can be moved onto the line showing maximum regeneration efficiency by controlling the throttle coefficient of the second variable throttle valve, the operating point of the motor is moved onto the line showing maximum regeneration efficiency.

FIG. 1 is a conceptual diagram of a cylinder device according to one embodiment. FIG. 2 is a model diagram showing the relationship between the flow rate and the differential pressure of the cylinder device in one embodiment. FIG. 3 is a graph showing the rotational speed of the motor as a function of the flow rate through the pump, and the torque of the motor as a function of the pressure difference (pressure loss) as the liquid passes through the pump. FIG. 4 is a diagram showing the range of the motor rotation speed and the torque that can be output. FIG. 5 is a diagram showing the configuration of the controller. FIG. 6 is a diagram showing the configuration of the regenerative control unit.

The present invention will be described below based on the embodiment shown in the figures. As shown in FIG. 1, the cylinder device A in one embodiment is configured with a hydraulic cylinder 1 and a controller 11.

The components of the cylinder device A will be described in detail below. As shown in FIG. 1, the hydraulic cylinder 1 is configured with a cylinder 2, a piston 3 that is movably inserted into the cylinder 2 and divides the cylinder 2 into two working chambers R1 and R2, a first flow path 4 and a second flow path 5 that are parallel to each other and communicate the working chambers R1 and R2, a first variable throttle valve 6 provided in the first flow path 4, a second variable throttle valve 7 provided in series in the second flow path 5, and a bidirectional discharge pump 9 driven by a motor 8, and the cylinder 2 is filled with liquid and sealed. The piston 3 is connected to a rod 10 that is movably inserted into the cylinder 2, and in the case of this hydraulic cylinder 1, the rod 10 protrudes from both ends of the cylinder 2, making it a so-called double-rod type cylinder device.

When the hydraulic cylinder 1 is applied to a vehicle, the cylinder 2 is connected to one of the sprung and unsprung members of the vehicle, and the rod 10 is connected to the other of the sprung and unsprung members, and is interposed between the sprung and unsprung members. When the hydraulic cylinder 1 is applied to a vehicle and used, it exerts a thrust to suppress vibrations of the vehicle body, which is the sprung member, and the vehicle wheels, which are the unsprung members. In this document, the hydraulic cylinder 1 is said to extend when the rod 10 moves upward in FIG. 1 relative to the cylinder 2 together with the piston 3, and conversely, the hydraulic cylinder 1 is said to contract when the rod 10 moves downward in FIG. 1 relative to the cylinder 2 together with the piston 3. Although the hydraulic cylinder 1 is configured as a double-rod type in the illustrated example, it may be configured as a single-rod type.

The inside of the cylinder 2 is divided by the piston 3 into an extension side working chamber R1 at the top in FIG. 1 and a compression side working chamber R2 at the bottom in FIG. 1, as described above, and each of the working chambers R1, R2 is filled with a liquid such as hydraulic oil. The liquid may be other liquids such as water or an aqueous solution in addition to hydraulic oil. As described above, the hydraulic cylinder 1 is a double-rod type hydraulic cylinder, and even if the rod 10 moves up and down in FIG. 1 together with the piston 3 relative to the cylinder 2, the volume displaced by the rod 10 in the cylinder 2 does not change. Therefore, a reservoir is not provided to compensate for the volume of the rod 10 moving in and out of the cylinder 2, but an accumulator connected to the inside of the cylinder 2 may be provided to compensate for the volume change due to the temperature change of the liquid.

The pump 9 is set to be a bidirectional discharge type, and may be, for example, a vane pump, gear pump, axial pump, or the like, equipped with a rotating shaft (not shown) that can suck in and discharge fluid by rotating the rotating shaft, and conversely, can forcibly drive the rotating shaft by the flow of fluid. Furthermore, the rotating shaft of the pump 9 is connected to the motor 8, which can be driven by passing electricity, and which, when forcibly driven to rotate by input from the pump 9 side, generates electricity and generates torque to suppress the rotation of the pump 9. Various types of motors, whether DC or AC, can be used, for example, brushless motors, induction motors, synchronous motors, etc.

The hydraulic cylinder 1 can expand and contract spontaneously and generate thrust in the desired direction by driving the pump 9 with the motor 8 to rotate and send liquid from the extension side working chamber R1 to the compression side working chamber R2, or from the compression side working chamber R2 to the extension side working chamber R1 via the second flow path 5. When the hydraulic cylinder 1 is forcibly expanded or contracted by an external input, the pump 9, to which the torque of the motor 8 is transmitted, applies resistance to the flow of liquid moving from the extension side working chamber R1 to the compression side working chamber R2, or from the compression side working chamber R2 to the extension side working chamber R1, via the second flow path 5, generating thrust in a direction that prevents expansion or contraction.

Furthermore, when the hydraulic cylinder 1 is forcibly expanded or contracted, the motor 8 is forcibly driven via the pump 9 by the flow of liquid going back and forth through the second flow path 5, so that the kinetic energy of the liquid is converted into electrical energy by the motor 8, enabling power regeneration. The power regenerated by the motor 8 may be sent to an external device or stored in a capacitor.

In other words, the first variable throttle valve 6 is provided in the first flow path 4 that bypasses the pump 9 and communicates between the working chambers R1 and R2, and the second variable throttle valve 7 is provided in the second flow path 5 together with the pump 9. Therefore, the first variable throttle valve 6 is arranged in parallel with the second variable throttle valve 7 and the pump 9. The first variable throttle valve 6 and the second variable throttle valve 7 are capable of changing the throttle coefficient, which is the ratio of the passing flow rate to the pressure loss, by changing the opening degree and the valve passage length. Specifically, for example, various valves such as a variable choke and a variable orifice can be used, and the throttle coefficient can be changed by driving the valve body (not shown) with a drive source such as a solenoid or a motor. The drive source that changes the throttle coefficient in the first variable throttle valve 6 and the second variable throttle valve 7 is controlled by the controller 11.

Regarding the relative positioning of the pump 9 and the second variable throttle valve 7, the pump 9 may be disposed on either the working chamber R1 side or the working chamber R2 side. In addition, the fluid filled in the cylinder 2 may be any fluid, such as oil, water, an aqueous solution, or gas.

The hydraulic cylinder 1 configured in this manner can function as an actuator that expands and contracts by itself when power is supplied from the controller 11 to the motor 8 to drive the pump 9, but conversely, when the hydraulic cylinder 1 is expanded or contracted by an external force, the torque of the motor 8 suppresses the rotation of the pump 9; that is, the motor 8 is used in the braking region to generate a torque in the opposite direction to the rotation of the pump 9, and the motor 8, first variable throttle valve 6, and second variable throttle valve 7 work together to generate a damping force. When the motor 8 is used in the braking region, the rotational speed and torque of the motor 8 can be controlled by adjusting the throttle coefficients of the first variable throttle valve 6 and second variable throttle valve 7.

When a current is applied to the motor 8 to drive the pump 9, that is, when the motor 8 is used in the powering region to cause the hydraulic cylinder 1 to function as an actuator, the first variable throttle valve 6 is fully closed to prevent communication between the working chambers R1 and R2 via the first flow path 4, while the second variable throttle valve 7 is fully opened to prevent unnecessary resistance to the flow of liquid caused by the second variable throttle valve 7, resulting in energy loss.

Here, we will use the model diagram shown in Figure 2 to explain how to control the load (rotational speed and torque) of the motor 8 when the hydraulic cylinder 1 is extended or retracted by an external force. Note that the pump 9 provides resistance to the flow of liquid by the torque transmitted from the motor 8, causing pressure loss when the liquid passes through, so it can be treated as equivalent to a variable throttle valve. Therefore, in Figure 2, the motor 8 and pump 9 are shown as one variable throttle valve M.

Then, let ΔP be the pressure difference between one working chamber R1 and the other working chamber R2 when the hydraulic cylinder 1 is expanding or contracting, Q be the flow rate per unit time of the fluid flowing out from one working chamber R1 (hereinafter simply referred to as flow rate), C1 be the throttling coefficient which is the ratio of the flow rate q1 of the fluid passing through the first variable throttle valve 6 divided by the differential pressure (pressure loss) ΔP generated at the first variable throttle valve 6, C2 be the throttling coefficient which is the ratio of the flow rate q2 of the fluid passing through the second variable throttle valve 7 divided by the differential pressure (pressure loss) Δp2 generated at the second variable throttle valve 7, and C3 be the throttling coefficient which is the ratio of the flow rate q2 of the fluid passing through the variable throttle valve M consisting of the motor 8 and pump 9 divided by the differential pressure (pressure loss) Δpm generated at the variable throttle valve M, then the following formula 1 is obtained.

Here, if C=C2×C3/(C2+C3), then equation 1 can be written as equation 2 below.

Furthermore, since the total flow rate Q = q1 + q2 holds, and the differential pressure ΔP generated at the first variable throttle valve 6 is equal to the differential pressure generated across the entire variable throttle valve M consisting of the second variable throttle valve 7, the motor 8, and the pump 9, the following equation 3 holds:

Substituting Equation 3 into Equation 2 and summarizing, we obtain the following Equation 4.

As can be seen from the above formula 4, when the flow rate Q and the differential pressure ΔP are not changed, the flow rate q2 can be changed by changing the restriction coefficient C1.

In other words, by adjusting the flow rate q1 in the first variable throttle valve 6 that bypasses the pump 9 by changing the throttle coefficient C1, the flow rate q2 passing through the variable throttle valve M can be changed. For example, when the first variable throttle valve 6 is shifted from a fully closed state to a fully open state, the flow rate q2 can be increased or decreased to increase or decrease the rotation speed of the motor 8.

Furthermore, the flow rate at the second variable throttle valve 7 and the variable throttle valve M is q2, the overall differential pressure is ΔP, the differential pressure (pressure loss) at the variable throttle valve M is Δpm, and the composite throttle coefficient C of the second variable throttle valve 7 and the variable throttle valve M is C = C2 x C3 / (C2 + C3) as described above, so by focusing only on the second variable throttle valve 7 and the variable throttle valve M, the following equation 5 is obtained.

As can be seen from the above formula 5, when the flow rate q2 and the differential pressure ΔP are not changed, the differential pressure Δpm in the variable throttle valve M can be changed by changing the throttling coefficient C2.

In other words, by changing the throttling coefficient C2, it is possible to change the differential pressure Δpm that occurs when fluid passes through the pump 9. For example, when the second variable throttling valve 7 is shifted from a fully closed state to a fully open state, the differential pressure Δpm can be increased or decreased to increase or decrease the torque that must be borne by the motor 8.

The above will be explained with reference to the graph shown in FIG. 3, in which the rotation speed of the motor 8 corresponds to the flow rate through the pump 9 and the torque of the motor 8 corresponds to the differential pressure (pressure loss) when the fluid passes through the pump 9, with the flow rate Q and the differential pressure ΔP kept constant. By changing the throttling coefficient C2 of the second variable throttle valve 7, the torque to be borne by the motor 8 (burden torque) can be adjusted along the vertical axis, and by changing the throttling coefficient C1 of the first variable throttle valve 6, the rotation speed of the motor 8 can be adjusted along the horizontal axis. The burden torque of the motor 8 is the torque acting between the motor 8 and the pump 9, and can be considered as the torque that needs to be applied from the motor 8 to the pump 9 in order for the cylinder device A to output the desired thrust. Note that in this document, the term "burden torque" is used even when the hydraulic cylinder 1 is expanding and contracting spontaneously.

In detail, point a in Figure 3 shows the relationship between the rotation speed and the load torque of the motor 8 when the second variable throttle valve 7 is fully open to maximize the throttle coefficient C2 and the first variable throttle valve 6 is fully closed to minimize the throttle coefficient C1; point b shows the relationship between the rotation speed and the load torque of the motor 8 when the second variable throttle valve 7 is fully open to maximize the throttle coefficient C2 and the first variable throttle valve 6 is fully open to maximize the throttle coefficient C1; point c shows the relationship between the rotation speed and the load torque of the motor 8 when the second variable throttle valve 7 is fully closed to minimize the throttle coefficient C2 and the first variable throttle valve 6 is fully closed to minimize the throttle coefficient C1; and point d shows the relationship between the rotation speed and the load torque of the motor 8 when the second variable throttle valve 7 is fully closed to minimize the throttle coefficient C2 and the first variable throttle valve 6 is fully open to maximize the throttle coefficient C1. That is, by changing the throttle coefficients C1 and C2 of the first variable throttle valve 6 and the second variable throttle valve 7, the rotation speed and load torque of the motor 8 can be adjusted within the range surrounded by points a, b, c, and d.

Specifically, when the intersection of the rotation speed and the load torque of the motor 8 (the operating point of the motor) is at point a, increasing the throttling coefficient C1 of the first variable throttle valve 6 can shift the intersection toward point b, decreasing the throttling coefficient C2 of the second variable throttle valve 7 can shift the intersection toward point c, and increasing the throttling coefficient C1 of the first variable throttle valve 6 and decreasing the throttling coefficient C2 of the second variable throttle valve 7 can shift the intersection toward point d. In other words, by controlling the throttling coefficients of the first variable throttle valve 6 and the second variable throttle valve 7, the rotation speed and the load torque of the motor 8 can be controlled.

In addition, in the explanation of Figure 3, it is assumed that the flow rate Q and the differential pressure ΔP are constant, so there is no state in which the motor 8 is rotating despite its burden torque being 0, or in which there is a burden torque even though the rotational speed is 0. Therefore, the line connecting points b and d and the line connecting points d and c show the boundaries of the range in which the operating point of motor 8 can be, and the operating point of motor 8 will never be a value on these lines.

The range of the burden torque that can be output for any rotation speed of the motor 8 is, as shown in FIG. 4, a rotation speed torque coordinate system in which the vertical axis is the burden torque and the horizontal axis is the rotation speed, and is the region surrounded by an output limit line z1 consisting of a straight line parallel to the horizontal axis and a curve connected to the straight line in the first and second quadrants, and an output limit line z2 consisting of a straight line parallel to the horizontal axis and a curve connected to the straight line in the third and fourth quadrants. The straight lines on the output limit lines z1 and z2 indicate the upper limit of the burden torque of the motor 8, and are boundaries that arise due to the current being limited by a current limiter (not shown) provided in the controller 11. The curves on the output limit lines z1 and z2 also divide the burden torque region that can be generated at the rotation speed at that time and the burden torque region that cannot be generated, and are boundary lines determined by the characteristics of the power supply voltage (not shown), the induced power of the motor 8, etc. The sign of the torque in the forward direction of the motor 8 is positive and the sign of the torque in the reverse direction is negative, and the sign of the rotation speed when the motor 8 rotates in the forward direction is positive and the sign of the torque in the reverse direction is negative.

As can be seen from Figure 4, the higher the rotational speed of the motor 8 in each quadrant, the smaller the upper limit of the load torque that can be output. In other words, when the first variable throttle valve 6 is closed to block the first flow path 4 and the entire flow rate of the liquid passing through the working chambers R1 and R2 is passed to the pump 9, the higher the extension/retraction speed of the hydraulic cylinder 1, the higher the rotational speed of the motor 8 will be, and the smaller the load torque that can be output by the motor 8 will be.

In addition, in the second quadrant, where the rotation speed is negative and the burden torque is positive, and in the fourth quadrant, where the rotation speed is positive and the burden torque is negative, the motor 8 is operating in the braking region where power regeneration is possible, and in the first quadrant, where the rotation speed is positive and the burden torque is positive, and in the third quadrant, where the rotation speed is negative and the burden torque is negative, the motor 8 is operating in the powering region where power is consumed. Thus, the motor 8 is in a braking state when operating in the braking region, and in a powering state when operating in the powering region.

In Figure 4, the dashed line passing through the second and fourth quadrants where motor 8 is in a braking state is the maximum regenerative efficiency line, which shows the relationship between the rotational speed and torque at which motor 8's regenerative power is at its maximum, and is a straight line that passes through the origin and is tangent to the short-circuit curve that depicts the short-circuit characteristics of motor 8. The maximum regenerative efficiency line shows the relationship between the rotational speed and the maximum regenerative torque at which motor 8's regenerative power is at its maximum when motor 8 is operating in a braking state and rotating at a certain rotational speed, and if the operating point of motor 8 is on the maximum regenerative efficiency line, the regenerative power will be maximum at the rotational speed at that time. In this way, if the rotational speed of motor 8 is constant, regenerative efficiency will be maximized by locating the operating point of motor 8 on the maximum regenerative efficiency line.

Therefore, when the operating point of the motor 8 in the rotational speed torque coordinate system, in which the operating state of the motor 8 is in the braking state when the operating point of the motor 8 is in the second and fourth quadrants, is located in the hatched area X surrounded by the output limit line z1 and the vertical axis above the maximum regenerative efficiency line in the second quadrant, or when the operating point of the motor 8 is located in the hatched area Y below the maximum regenerative efficiency line in the fourth quadrant, if the throttling coefficient of the second variable throttle valve 7 is reduced to reduce the flow path of the second variable throttle valve 7, the pressure loss in the second variable throttle valve 7 increases and the torque borne by the motor 8 decreases, so that only the torque borne by the motor 8 can be reduced without changing the rotational speed of the motor 8. Then, if the throttling coefficient of the second variable throttle valve 7 is appropriately adjusted, the operating point of the motor 8 can be placed on the maximum regenerative efficiency line to maximize the regenerative power of the motor 8.

As shown in FIG. 5, the controller 11 includes a thrust control unit 20 that receives a thrust command indicating the target thrust of the hydraulic cylinder 1 from a higher-level control device and controls the motor 8, as well as a regeneration control unit 21 that controls the throttling coefficient of the second variable throttle valve 7 to improve the regeneration efficiency of the motor 8.

The thrust control unit 20 includes a current command generating unit 20a that, upon receiving a thrust command indicating the target thrust of the hydraulic cylinder 1 from a higher-level control device, determines a target current to be supplied to the motor 8 and outputs a current command indicating the target current, and a motor control unit 20b that, upon receiving the current command generated by the current command generating unit 20a, feeds back the current flowing through the motor 8 to control the current flowing through the motor 8 according to the target current. In this embodiment, the hydraulic cylinder 1 is applied to a vehicle, and the higher-level control device determines the thrust to be generated in the hydraulic cylinder 1 mainly for the purpose of suppressing the vibration of the vehicle body as a sprung member. The thrust command may be determined so as to enable not only the reduction of the vibration of the vehicle body but also the reduction of the vibration of the wheels as unsprung members. The thrust control unit 20 may also determine a thrust command by itself, rather than obtaining a thrust command from a higher-level control device, by detecting vibration information of the vehicle body, or the vehicle body and wheels in the vehicle, or by receiving such vibration information from the vehicle.

The current command generating unit 20a performs a calculation process to obtain a target current corresponding to the torque to be output to the motor 8 by feeding back the actual thrust generated by the hydraulic cylinder 1, and performing proportional, integral and differential compensation for the control deviation between the target thrust indicated by the thrust command and the actual thrust. The thrust of the hydraulic cylinder 1 is input to the current command generating unit 20a from an actual thrust detecting unit 25 including a pressure sensor 25a for detecting the pressure of the working chamber R1, a pressure sensor 25b for detecting the pressure of the working chamber R2, and a calculation unit 25c for multiplying the difference between the pressures of the working chambers R1 and R2 by the pressure receiving area of the piston 3 to obtain the thrust generated by the hydraulic cylinder 1. The current command generating unit 20a may be configured in any way as long as it can obtain a target current from the thrust command and generate a current command. In addition, since the thrust generated by the hydraulic cylinder 1 can be grasped by detecting the load provided on the rod 10, the actual thrust detecting unit 25 may be a sensor for detecting the load acting on the rod 10. In addition, the thrust control unit 20 may not detect the thrust actually output by the hydraulic cylinder 1, but may instead detect the pressure and load described above, and may include an observer that detects state quantities of the hydraulic cylinder 1, such as the throttle coefficients of the first variable throttle valve 6 and the second variable throttle valve 7, the rotation speed of the motor 8, and the torque, and estimates the thrust of the hydraulic cylinder 1 from the state quantities. The actual thrust of the hydraulic cylinder 1 may be estimated from information from an acceleration sensor attached to the vehicle body and the axle, or the actual thrust of the hydraulic cylinder 1 may be estimated using information from a sensor used for purposes other than the control of the cylinder device A. In this case, the current command generation unit 20a may feed back the thrust estimated by the observer to obtain the target current. The motor control unit 20b may be provided with a drive circuit suitable for current control of the motor 8 depending on the type of the motor 8, and may be capable of controlling the current of the motor 8 according to the current command.

The regenerative control unit 21 includes a first variable throttle valve control unit 22 that controls the throttle coefficient of the first variable throttle valve 6, and a second variable throttle valve control unit 23 that controls the throttle coefficient of the second variable throttle valve 7, and controls the second variable throttle valve 7 while monitoring the rotation speed and torque of the motor 8. The rotation speed of the motor 8 may be obtained from the rotation position information of the rotor detected by a sensor such as a resolver (not shown) that can detect the rotation position of the rotor. The rotation speed of the motor 8 may be estimated from the stroke displacement information of the suspension. The torque of the motor 8 is proportional to the current flowing through the motor 8 when the motor 8 is a DC motor or a motor equivalent to a DC motor, so the current can be regarded as the torque as it is, and since the motor control unit 20b includes a sensor that detects the current of the motor 8, the current value can be obtained from the motor control unit 20b and used as the torque of the motor 8. The regenerative control unit 21 may include a sensor that detects the rotation speed of the motor 8, and a sensor that detects the torque of the motor 8 or a sensor that detects the current of the motor 8 separately. The regenerative control unit 21 sequentially captures the rotation speed and torque of the motor 8 at a predetermined calculation cycle and processes the captured rotation speed and torque. The regenerative control unit 21 processes the torque of the motor 8, but as described above, the current flowing through the motor 8 can be considered as torque, so the current flowing through the motor 8 can be treated and processed as torque.

Here, when the motor 8 is operating in a braking state, the higher the rotation speed of the motor 8, the greater the regenerative power of the motor 8, so it is better to reduce the flow area of the first variable throttle valve 6 as much as possible and increase the flow rate of the liquid passing through the second flow path 5. Also, when the motor 8 is operating in a powered state, if the flow area of the first variable throttle valve 6 is large, the pressure difference between the working chambers R1 and R2 will be small, the thrust generated by the hydraulic cylinder 1 will be small, and the energy consumed by the pump 9 will also be high, so it is better to reduce the flow area of the first variable throttle valve 6 as much as possible and increase the flow rate of the liquid passing through the second flow path 5. In this way, regardless of whether the operating state of the motor 8 is a braking state or a powered state, it is preferable for the flow area of the first variable throttle valve 6 to be small. Therefore, the first variable throttle valve control unit 22 basically fixes the throttle coefficient of the first variable throttle valve 6 to a predetermined small value regardless of the operating state of the motor 8, and controls the first variable throttle valve 6 to close or reduce the flow path area, thereby limiting the flow rate of the liquid passing through the first flow path 4 to zero or a very small amount.

The second variable throttle valve control unit 23 performs regenerative control to reduce the throttling coefficient of the second variable throttle valve 7 so that the operating point of the motor 8 is located on the maximum regenerative efficiency line when the operating state of the motor 8 is in the braking state and the operating point of the motor 8 is in the second quadrant and is located in the region X where the torque is greater than the maximum regenerative efficiency line, or the operating point of the motor 8 is in the fourth quadrant and is located in the region Y where the torque is smaller than the maximum regenerative efficiency line, under the condition that the motor 8 is in the braking state. On the other hand, when the conditions for performing regenerative control are not met even in the braking state and when the motor 8 is in the powered state, the second variable throttle valve control unit 23 maximizes the throttling coefficient of the second variable throttle valve 7 so as not to impede the passage of the liquid discharged by the pump 9, since the second variable throttle valve 7 becomes a resistance to the operation of the pump 9.

Therefore, the second variable throttle valve control unit 23 is configured to include a filter processing unit 30 including a first filter 30a that removes components equal to or higher than the unsprung resonance frequency from the rotation speed of the motor 8 and outputs a filtered rotation speed, and a second filter 30b that removes components equal to or higher than the unsprung resonance frequency from the torque of the motor 8 and outputs a filtered torque, a braking state determination unit 31 that determines whether the motor 8 is in a braking state based on the filtered rotation speed and the filtered torque, an operating point position determination unit 32 that determines whether the operating point of the motor 8 is in region X or region Y, a throttling coefficient calculation unit 33 that calculates a throttling coefficient of the second variable throttle valve 7 based on the determination results of the braking state determination unit 31 and the determination results of the operating point position determination unit 32, the rotation speed of the motor 8, and the thrust of the hydraulic cylinder 1, and a drive circuit 34 that receives a command indicating the throttling coefficient calculated by the throttling coefficient calculation unit 33 and controls the current supplied to a drive source (not shown) in the second variable throttle valve 7.

The filter processing unit 30 includes a first filter 30a that removes components of the rotation speed of the motor 8 that are equal to or higher than the unsprung resonance frequency band and outputs a filtered rotation speed, and a second filter 30b that removes components of the torque of the motor 8 that are equal to or higher than the unsprung resonance frequency band and outputs a filtered torque. The filter processing unit 30 processes the rotation speed and torque of the motor 8 that are input sequentially, and outputs signals of the filtered rotation speed and filtered torque.

When the hydraulic cylinder 1 is used by being interposed between the vehicle body, which is the sprung member, and the wheels, which are the unsprung members of the vehicle, the hydraulic cylinder 1 expands and contracts due to the relative movement between the vehicle body and the wheels, and vibrations of the vehicle body and wheels are input to the hydraulic cylinder 1. The vibrations input to the hydraulic cylinder 1 also change the flow rate of liquid passing through the pump 9 in the second flow path 5, and so the rotation speed and torque of the motor 8 also fluctuate. Therefore, high-frequency components in the resonant frequency band of the wheels and high-frequency noise are superimposed on the rotation speed and torque of the motor 8 before processing by the filter processing unit 30.

As a result, if processing by the filter processing unit 30 is not performed, the operating point of the motor 8 will shift in an oscillatory manner at high frequencies, and hunting may occur in subsequent processing such as determining the operating state of the motor 8. For this reason, in this embodiment, the first filter 30a and the second filter 30b are bandpass filters that are capable of extracting the resonant frequency components of the sprung member. Since the resonant frequency band of the sprung member is approximately 1 Hz to 2 Hz, the first filter 30a and the second filter 30b are set to have characteristics that enable them to extract components of 1 Hz to 2 Hz.

In this way, in the cylinder device A of this embodiment, the rotation speed and torque of the motor 8 are processed by the filter processing unit 30 to remove high-frequency components equal to or higher than the unsprung resonance frequency from the rotation speed and torque of the motor 8, so that the braking state of the motor 8 can be accurately grasped according to the vibration of the sprung member in the vehicle, and the throttling coefficient of the second variable throttle valve 7 can be appropriately controlled by the second variable throttle valve control unit 23. Note that the first filter 30a and the second filter 30b in the filter processing unit 30 are filters that extract components in the sprung resonance frequency band, but they may be low-pass filters that can remove at least components equal to or higher than the unsprung resonance frequency band. In this way, even if the first filter 30a and the second filter 30b are low-pass filters that can remove components equal to or higher than the unsprung resonance frequency band, the vibration and noise of the unsprung member can be removed from the rotation speed and torque signals, so that the braking state of the motor 8 can be accurately grasped, and the throttling coefficient of the first variable throttle valve 6 can be appropriately controlled by the first variable throttle valve control unit 22. By providing the first filter 30a and the second filter 30b in the filter processing unit 30, the braking state of the motor 8 can be grasped with high accuracy, but it is also possible to omit the first filter 30a and the second filter 30b.

Then, the braking state determination unit 31 determines whether the motor 8 is in a braking state based on the filtered rotation speed and the filtered torque. Specifically, the braking state determination unit 31 determines which quadrant in FIG. 4 the operating point of the motor 8 is in, based on the sign of the filtered rotation speed and the sign of the filtered torque, and determines whether the motor 8 is in a braking state or a powering state. After determining the operating state of the motor 8, the braking state determination unit 31 inputs the determination result to the throttling coefficient calculation unit 33.

In detail, if the filtered rotation speed is positive and the filtered torque is positive, that is, if the filtered rotation speed is ωf and the filtered torque is Tf, and ωf ≧ 0 and Tf ≧ 0, the braking state determination unit 31 determines that the operating point of the motor 8 is in the powering region of the first quadrant in FIG. 4, and determines that the operating state of the motor 8 is a powering state in the first quadrant.

Furthermore, if the filtered rotation speed is negative and the filtered torque is positive, that is, if ωf<0 and Tf≧0, the braking state determination unit 31 determines that the operating point of the motor 8 is in the braking region of the second quadrant in FIG. 4, and determines that the operating state of the motor 8 is a braking state in the second quadrant.

Furthermore, if the filtered rotation speed is negative and the filtered torque is negative, and ωf<0 and Tf<0, the braking state determination unit 31 determines that the operating point of the motor 8 is in the powering region of the third quadrant in FIG. 4, and determines that the operating state of the motor 8 is a powering state in the third quadrant.

Then, if the filtered rotation speed is positive and the filtered torque is negative, that is, if ωf≧0 and Tf<0, the braking state determination unit 31 determines that the operating point of the motor 8 is in the braking region of the fourth quadrant in FIG. 4, and determines that the operating state of the motor 8 is a braking state in the fourth quadrant.

In this way, the braking state determination unit 31 determines whether the value of ωf is positive or negative, and whether the value of Tf is positive or negative, and determines which of the four quadrants the operating point of the motor 8 falls into, and thus determines whether the operating state of the motor 8 is in a braking state or a powering state.

The operating point position determination unit 32 determines whether the operating point of the motor 8 is in region X or region Y based on the filtered rotation speed and filtered torque, and inputs the determination result to the throttling coefficient calculation unit 33.

Here, assuming that motor 8 is a brushless DC motor, the q-axis voltage applied to the windings of motor 8 is vq, the q-axis current of the windings of motor 8 is iq, the inductance of the windings of motor 8 is L, the resistance of the windings of motor 8 is R, the torque constant of motor 8 is Km, the coefficient for converting the rotational speed of motor 8 to angular speed is Kω, the rotational speed of motor 8 is ωm, the torque generated by motor 8 is Tm, the burden torque of motor 8 is Tl, the viscous resistance of motor 8 is Cm, and motor 8 is in a steady state with no change in rotational speed, the rotation equation, torque equation, and equation of motion for motor 8 can be expressed by the following

Equations

6, 7, and 8, respectively.

Moreover, the power P input to the motor 8 from a power source not shown in the figure is expressed by the following formula 9.

When the sign of the power P is positive, it indicates that the motor 8 consumes power, and here, substituting Equation 6 into Equation 9 gives Equation 10.

By transforming equation 10 and completing the square, we obtain equation 11.

It can be seen from the above formula 11 that when the first term in formula 11 becomes 0, the value of the power P becomes minimum and takes a negative value. When the value of the power P becomes negative, this means that the motor 8 is generating power and regenerating power. In other words, when the rotation speed of the motor 8 is ωm, the current iqmax that maximizes the regenerative power of the motor 8 is calculated by the following formula 12.

By substituting Equation 12 into Equation 11, the maximum value Pmax of the regenerative power at a certain rotation speed can be obtained by the following Equation 13.

Furthermore, by substituting Equation 7 and Equation 12 into Equation 8, the relationship between the burden torque Tm of the motor 8 and the rotation speed of the motor 8 is expressed by the following Equation 14.

Equation 14 shows the relationship between the rotation speed and burden torque of motor 8 when the regenerative power is maximized, and is nothing but an equation showing the line of maximum regenerative efficiency. In other words, the burden torque on the left side of equation 14 is the maximum regenerative torque that maximizes the regenerative power at the rotation speed of motor 8 at that time. Therefore, when the measured values of the rotation speed and torque of motor 8 are substituted into equation 15, if equation 15 holds, it indicates that the operating point of motor 8 is in area X or area Y.

Therefore, the operating point position determination unit 32 substitutes the filtered rotation speed and the filtered torque into equation 15, and determines that the operating point of the motor 8 is in area X or area Y if equation 15 holds.

When the braking state determination unit 31 determines that the operating state of the motor 8 is in a braking state and the operating point position determination unit 32 determines that the operating point of the motor 8 is in area X or area Y, the throttling coefficient calculation unit 33 calculates the throttling coefficient of the second variable throttling valve 7 required to position the operating point of the motor 8 on the line with maximum regenerative efficiency based on the rotational speed of the motor 8 and the thrust generated by the hydraulic cylinder 1.

Assuming that the motor 8 is in a steady state and that there is no change in the rotational speed of the motor 8, the displacement volume of the pump 9 is Vp, the pressure in the working chamber R1 above the hydraulic cylinder 1 is pu, the pressure in the working chamber R2 below the hydraulic cylinder 1 is pl, the throttling coefficient of the second variable throttle valve 7 is fv2, and the current flowing through the windings of the motor 8 is im, the following equation 16 is established.

In addition, if the thrust generated by the hydraulic cylinder 1 is fa and the pressure-receiving area of the piston 3 is A, the thrust fa can be expressed by the following equation 17.

By substituting equations 12 and 17 into equation 16 and rearranging it, equation 18 is obtained for determining the throttle coefficient fv2 that places the operating point of the motor 8 on the maximum regenerative efficiency line.

Since the values in Equation 18 other than the rotation speed ωm of the motor 8 and the thrust fa generated by the hydraulic cylinder 1 are known, it can be understood that the value of the throttling coefficient fv2 changes with the rotation speed ωm and thrust fa as parameters. Therefore, by detecting the rotation speed ωm and the thrust fa, it is possible to determine the throttling coefficient fv2 that places the operating point of the motor 8 on the maximum regenerative efficiency line. Then, when the throttling coefficient of the second variable throttle valve 7 is made to match the throttling coefficient fv2 determined as described above, the torque of the motor 8 matches the maximum regenerative torque, and the operating point of the motor 8 is placed on the maximum regenerative efficiency line, thereby maximizing the regenerative efficiency.

Therefore, when the braking state determination unit 31 determines that the operating state of the motor 8 is in the braking state and the operating point position determination unit 32 determines that the operating point of the motor 8 is in area X or area Y, the throttle coefficient calculation unit 33 substitutes the rotation speed of the motor 8 and the thrust determined by the actual thrust detection unit 25 into equation 18 to determine the throttle coefficient fv2 of the second variable throttle valve 7 that places the operating point of the motor 8 on the maximum regenerative efficiency line. Then, when the throttle coefficient calculation unit 33 determines the throttle coefficient fv2 of the second variable throttle valve 7 that places the operating point of the motor 8 on the maximum regenerative efficiency line, it sets the determined throttle coefficient fv2 as the target throttle coefficient of the second variable throttle valve 7.

On the other hand, if the braking state determination unit 31 determines that the operating state of the motor 8 is in a powering state, or if the operating point position determination unit 32 determines that the operating point of the motor 8 is not in region X or region Y, the throttling coefficient calculation unit 33 sets the maximum throttling coefficient that can be achieved in controlling the second variable throttling valve 7 as the target throttling coefficient so as not to interfere with the operation of the pump 9.

The target throttle coefficient calculated by the throttle coefficient calculation unit 33 is input to the drive circuit 34. The drive circuit 34 adjusts the throttle coefficient of the second variable throttle valve 7 by applying a current to a drive source (not shown) of the second variable throttle valve 7 so that the throttle coefficient of the second variable throttle valve 7 matches the target throttle coefficient.

In this way, when the operating state of the motor 8 is in a braking state and the operating point of the motor 8 is in the second quadrant and located in region X above the maximum regenerative efficiency line, or when the operating point of the motor 8 is in the fourth quadrant and located in region Y below the maximum regenerative efficiency line, the regenerative control unit 21 performs regenerative control to reduce the throttling coefficient of the second variable throttle valve 7. When the regenerative control unit 21 performs regenerative control to reduce the throttling coefficient of the second variable throttle valve 7, the torque of the motor 8 decreases and coincides with the maximum regenerative torque while the rotation speed of the motor 8 remains constant, and the operating point of the motor 8 moves onto the maximum regenerative efficiency line. When the operating point of the motor 8 moves onto the maximum regenerative efficiency line due to the regenerative control of the regenerative control unit 21, the regenerative power of the motor 8 becomes maximum at the rotation speed at that time, and the regenerative efficiency improves.

The controller 11 configured as described above controls the throttling coefficient of the second variable throttle valve 7 according to the flowchart shown in FIG. 6. First, the controller 11 detects the rotation speed of the motor 8 and the torque flowing to the motor 8 (step F1). Next, the controller 11 filters the rotation speed and torque of the motor 8 to obtain the filtered rotation speed and filtered torque (step F2).

Furthermore, the controller 11 judges whether the operating state of the motor 8 is in a braking state from the filtered rotation speed and the filtered torque (step F3). Next, if the operating state of the motor 8 is in a braking state, the controller 11 judges whether the operating point of the motor 8 is in the region X or region Y (step F4). Then, if it is judged in the judgments of steps F3 and F4 that the motor 8 is in a braking state and that the operating point of the motor 8 is in the region X or region Y, the controller 11 calculates the throttling coefficient of the second variable throttle valve 7 that puts the operating point of the motor 8 on the maximum regenerative efficiency line (step F5), and sets the target throttling coefficient to the calculated throttling coefficient (step F6). If it is judged in the judgments of steps F3 and F4 that the motor 8 is in a powered state or that the operating point of the motor 8 is not in the region X or region Y, the controller 11 sets the target throttling coefficient to the maximum throttling coefficient that the second variable throttle valve 7 can control (step F7). Once the target throttle coefficient has been set, the controller 11 supplies current from the drive circuit 34 to the drive source of the second variable throttle valve 7 to control the throttle coefficient of the second variable throttle valve 7 to the target throttle coefficient (step F8).

The controller 11 repeatedly executes the above process to control the throttle coefficient of the second variable throttle valve 7 so as to increase the regenerative power when the motor 8 is in a braking state.

In addition, except for the drive circuit in the thrust control unit 20, the

pressure sensors

25a, 25b in the actual thrust detection unit 25, the drive circuit in the first variable throttle valve control unit 22, and the drive circuit 34 in the second variable throttle valve control unit 23, the hardware resources of the controller 11 may be configured to include, although not shown in the figure, an interface for inputting signals of thrust commands, the rotational speed and torque (current) of the motor 8, and the pressure in the cylinder 2, a storage device such as a ROM (Read Only Memory) in which programs used for the processing required to control the motor 8, the first variable throttle valve 6, and the second variable throttle valve 7 are stored, an arithmetic unit such as a CPU (Central Processing Unit) that executes processing based on the programs, and a storage device such as a RAM (Random Access Memory) that provides a storage area for the CPU, and each part of the thrust control unit 20 and the regenerative control unit 21 in the controller 11 can be realized by the execution of the programs by the CPU. Additionally, the controller 11 may be realized by an analog electronic circuit, instead of by a CPU executing the program.

As described above, the cylinder device A of this embodiment includes a hydraulic cylinder 1 having a cylinder 2, a piston 3 that is movably inserted into the cylinder 2 and divides the inside of the cylinder 2 into two working chambers R1 and R2, a first flow path 4 and a second flow path 5 that are parallel to each other and communicate the working chambers R1 and R2, a first variable throttle valve 6 provided in the first flow path 4, a second variable throttle valve 7 provided in series in the second flow path 5, and a bidirectional discharge type pump 9 driven by a motor 8, and a controller 11 that controls the first variable throttle valve 6, the second variable throttle valve 7, and the motor 8. In a rotational speed torque coordinate system in which the operating state of the motor 8 is in a braking state when the operating point of the motor 8 is in the second quadrant and in the fourth quadrant, when the operating point of the motor 8 is in an area X where the torque is greater than the maximum regenerative efficiency line in the second quadrant, or when the operating point of the motor 8 is in an area Y where the torque is smaller than the maximum regenerative efficiency line in the fourth quadrant, the throttle valve 11 calculates a target throttle coefficient of the second variable throttle valve 7 that places the operating point of the motor 8 on the maximum regenerative efficiency line based on the rotational speed of the motor 8 and the thrust generated by the hydraulic cylinder 1, and controls the second variable throttle valve. According to the cylinder device A configured in this way, when the motor 8 is in a braking state and power regeneration is possible, and a situation is reached in which the operating point of the motor 8 can be moved onto the maximum regenerative efficiency line by controlling the throttle coefficient of the second variable throttle valve 7, the throttle coefficient of the second variable throttle valve 7 is adjusted to the target variable throttle coefficient, and the operating point of the motor 8 is moved onto the maximum regenerative efficiency line. Therefore, with cylinder device A, it is possible to determine the conditions under which the operating point of motor 8 can be moved onto the line of maximum regenerative efficiency, and actually maximize the regenerative power.

The controller 11 in the cylinder device A of this embodiment also includes a braking state determination unit 31 that determines whether the motor 8 is in a braking state based on the rotation speed and torque of the motor 8. With the cylinder device A configured in this manner, it is possible to accurately determine whether the operating point of the motor 8 is in the second or fourth quadrant in the rotation speed torque coordinate system, where the motor 8 is in a braking state, based on the rotation speed and torque of the motor 8, and therefore it is possible to accurately determine one condition for executing regenerative control that improves regenerative efficiency by adjusting the throttling coefficient of the second variable throttle valve 7.

In addition, in the cylinder device A of this embodiment, the controller 11 is equipped with a first filter 30a that removes components equal to or higher than the unsprung resonance frequency of the vehicle from the rotation speed of the motor 8, a second filter 30b that removes components equal to or higher than the unsprung resonance frequency of the vehicle from the torque of the motor 8, a braking state determination unit 31 that determines whether the motor 8 is in a braking state based on the filtered rotation speed and the filtered torque, and an operating point position determination unit 32 that determines whether the operating point of the motor 8 is in the region X or region Y based on the filtered rotation speed and the filtered torque. According to the cylinder device A configured in this manner, components equal to or higher than the high-frequency unsprung resonance frequency are removed from the rotation speed and torque of the motor 8, so that the braking state and the position of the operating point of the motor 8 can be accurately grasped according to the vibration of the sprung member of the vehicle, and the throttling coefficient of the second variable throttle valve 7 can be appropriately controlled.

Although the preferred embodiment of the present invention has been described in detail above, modifications, variations, and changes are possible without departing from the scope of the claims.

1: hydraulic cylinder, 2: cylinder, 3: piston, 4: first flow path, 5: second flow path, 6: first variable throttle valve, 7: second variable throttle valve, 8: motor, 9: pump, 11: controller, 31: braking state determination unit, A: cylinder device, R1, R2: working chamber

Claims

A cylinder device,
a hydraulic cylinder having a cylinder, a piston movably inserted into the cylinder to divide the inside of the cylinder into two working chambers, a first flow passage and a second flow passage arranged in parallel with each other and communicating the working chambers with each other, a first variable throttle valve provided in the first flow passage, a second variable throttle valve provided in series in the second flow passage, and a two-way discharge pump driven by a motor;
a controller for controlling the first variable throttle valve, the second variable throttle valve, and the motor,
the controller determines a target throttle coefficient of the second variable throttle valve that places the operating point of the motor on the maximum regenerative efficiency line based on the rotational speed of the motor and the thrust generated by the hydraulic cylinder, and controls the second variable throttle valve when the operating point of the motor is located in a region of greater torque than the maximum regenerative efficiency line in the second quadrant, or when the operating point of the motor is located in a region of less torque than the maximum regenerative efficiency line in the fourth quadrant, in a rotational speed-torque coordinate system in which the operating state of the motor is in a braking state when the operating point of the motor is in the second or fourth quadrant.
The cylinder device according to claim 1,
The controller:
a braking state determination unit that determines whether the motor is in a braking state based on a rotation speed and a torque of the motor.
The cylinder device according to claim 2,
The controller:
a first filter that removes components equal to or higher than an unsprung resonance frequency of a vehicle from the rotation speed of the motor and outputs a filtered rotation speed;
a second filter that removes components having frequencies equal to or higher than an unsprung resonance frequency of the vehicle from the torque of the motor and outputs a filtered torque;
an operating point position determination unit that determines whether an operating point of the motor is in a region in the second quadrant where the torque is greater than a maximum regenerative efficiency line or in a region in the fourth quadrant where the torque is smaller than a maximum regenerative efficiency line, based on the filtered rotation speed and the filtered torque;
The braking state determination unit determines whether the motor is in a braking state based on the filtered rotation speed and the filtered torque.