Regenerative shock absorber using cylindrical cam and slot motion conversion

The introduction

Energy feedback damper is a new type of regenerative shock absorber (RSA). With the improvement of environmental protection, there are many challenges in our life. The first challenge is the environmental pollution caused by the growing concern about the environment and the depletion of natural resources such as oil. Therefore, the mechanical energy generated in the proposed process is converted into electrical energy (Chen and Zhang 2014; https://en.wikipedia.org/). The second challenge is the cost. From the invention of the car until now, engineers have worked to improve the car’s design, but some expenses are borne by the user such as fuel, battery, and oil (Gillespie 1992). The third challenge is sustainability, and sustainable energy is energy that serves our needs in the present without affecting the future, such as hydropower, solar energy, wind, waves, bioenergy, and technologies designed to improve energy efficiency (Faiz and Nematsaberi 2017). The fourth challenge is performance. RSA renewable energy harvesting has become a research hot spot; helical gears were used with bevel clutches and a DC generator (Moritz 2014).

There are other types of RSA they work by different ways and have different features such as converting shock oscillation and vibration into unidirectional driving rotation (Li et al. 2013a, 2014; Maravandi and Moallem 2015). The RSA has the crucial functions of supporting the vehicle body and buffering vibrations produced by the road surfaces (Castillo et al. 2013; Salman et al. 2018). There are many types of suspension system equipment, including magnetic suspense, and the advantage of this type is that it can achieve high-speed driving without friction (Qualifying and Report 2009; Ryosuke et al. 2017; Tan et al. 2017). The coil spring is usually used in the suspension system of vehicles. It is a steel rod that is coiled into a spiral. It has great flexibility. If some weight is applied, it will shrink, and the heavier the weight, the greater the shrinkage (Singh and Srilatha 2018; Wang et al. 2017). The researchers pointed out that the vehicle’s suspension plays an important role in the safety and maintenance of vehicles (Zhang et al. 2015). Currently, suspension systems are classified as the basis of electric energy extraction mechanisms in vehicles (Studies and Xu 2013). A good suspension system should ensure that the vehicle will be stable in every maneuver (Goodarzi and Khajepour 2017). The suspension system affects the driver’s control of the car and the occupants’ comfort (Raja et al. 2017). With the increase of the world’s population, the energy crisis is becoming more serious. Many vehicles are stranded in driving, which brings pressure on the supply of fossil fuels (Salman et al. 2018). Researchers have improved the car mechanical transmission system and which very important to help reduce the amount of pollution in this era (Angelopoulou et al. 2019; Stevic and Radovanovic 2012). Energy consumption tests are also in different ways and at different speeds (Yao et al. 2016). There are two types of energy harvesting. One uses solar radiation as an energy source, and the other uses mechanical energy through a car’s load (Du et al. 2019; Pei et al. 2021). Zhang (Zhang, Wang, and John 2018) stated that the fuel energy dissipated to drive the wheels’ accounts for up to 22.5% of the total fuel energy consumed, ranking it the second following engine heat losses of 75.2% (Ahmad, Abdul Mujeebu, and Farooqi 2015). The electricity that charges and fuels battery-electric and plug-in hybrid vehicles comes from power grids, which rely on a range of fossil fuel sources to clean renewable energy.

The main contents of this new RSA are the long slanting holes, gearboxes, and steering blocks as shown in Figure 2 the sliding way is provided with a long vertical slot, and the connecting rod passes the long vertical slot and the long slanted slot on the outer upper cylinder body. The bevel gears in the gearbox are installed at both ends of the horizontal shaft and are joined together with the bevel gears with sweep clutches (Tank, Patel, and Sanghavi 2016). Although the shock spring can filter the road’s vibration when passing over the uneven road, the spring itself will vibrate. The RSA role is to suppress the reciprocating motion of the spring (Ankitha and Rupa Sri 2021; Bi and Song 2016; Konieczny 2016; Tata and Tata 2012). It is used to suppress the shock of the spring rebound after shock absorption and the road’s impact and widely used in automobiles to accelerate the vibration attenuation of frame and body (Li et al. 2013b; Zhang et al. 2017). After absorbing the impact, the elastic element will produce vibration and even cause resonance, so the vibration should be reduced as far as possible. The vehicle wheels are exposed to shocks while traveling due to hitting bumps or gaps in the road, resulting in shocks transmitted to the vehicle’s structure and then the passenger or driver felt it. All of this comes from the lifespan of the wheel (Advantages 2010; Barton and Fieldhouse 2018; Zou et al. 2017, 2019). The generator is one of the most important parts of RSA. Converts mechanical energy into electrical energy; this paper uses a stepper motor to provide power (Zhang et al. 2016). After the power input unit and the power transmission unit of the RSA power feed, the RSA power feed can drive the motor to always rotate in one direction the DC brushless motor does not require maintenance, so the power supply shock absorber power unit designed in this article uses the DC brushless motor. This type of RSA is not only used in cars, but also it can be used in buses because it has the function of energy recovery. It has a simple and new structure, simple production, and a low cost. With the tilted long-slot steering mechanism adopted by the present invention, the reciprocating linear motion is converted into a rotation. The bidirectional rotation is converted into a one-way rotation of the main generator shaft through the gear set to collect the vibration energy generated during the vehicle driving and improve the utilization rate energy.

System design

To overcome the problems found in previous vehicle RSA, we proposed an automobile RSA, which is characterized in the upper end of the cylindrical inner upper cylinder block and is fixed with an upper baffle. The upper mounting ring is fixed above the upper baffle. A thrust bearing is set between the lower end of the inner upper cylinder block and the guide frame’s upper surface. The thrust bearing is bidirectional. There is a rotational fit clearance between the outer surface of the inner upper cylinder block and the sleeve structure’s inner surface. The two sides of the outer upper cylinder body correspondingly provide a long-inclined slot, and the lower end is provided with flanging. The angle between the two inclined slots and the horizontal direction is 45°. The return spring is fixed between the upper baffle and the flanging. The connecting rod passes through the through-hole under the guide frame, the long vertical slot on the slide way, and the inclined long slot on the outer upper cylinder body. The shaft stop is fixed at both ends. The two ends of the connecting rod can also be provided with rolling bearings (Figure 1).

Figure 1:

The flow chart for the proposed new regenerative shock absorber (RSA).

Compared with the existing technology, this type of RSA will improve machine efficiency, reduce maintenance costs, furthermore, it will reduce noise pollution and reduce energy costs. With the tilted long-slot steering mechanism adopted by the present invention, the reciprocating linear motion is converted into a rotation. The bidirectional rotation is converted into a one-way rotation of the main generator shaft through the gear set to collect the vibration energy generated during the vehicle driving and improve the utilization rate energy.

In Figure 2 the guide frame’s outer and inner sides of the slide way are sliding fit gaps, while the two sides of the guide block and the long vertical slot, the connecting rod, the long vertical hole, and the inclined long slot are also sliding fit gaps. The utility model is provided with a fixing plate. The periphery of the fixing plate is provided with four uniformly distributed circular through-holes. The flanging of the outer upper cylinder block and the outer lower cylinder blocks flanging is provided through a slot corresponding to the circular through a slot on the fixing plate. The bolts fasten them. The upper end of the gearbox is fixedly connected with the lower end of the fixed plate. A thrust bearing is arranged between the lower surface of the base and the fixed plate’s upper surface. The vertical shaft’s upper end in the bevel gear passes through the vertical slot on the shaft shoulder on the base and is fastened with the shaft shoulder on the base through the pin. The vertical shaft is connected with the main shaft of the generator. The generator, the rectifier voltage regulating the circuit, and the supercapacitor constitute power generation and energy storage design. A fastening bolt is arranged between the generator and the lower bottom of the gearbox. The two ends of the horizontal shaft are provided with retaining rings.

Figure 2:

Show the regenerative shock absorber (RSA) with details

Suspension vibration input design

The RSA is installed between the vehicle body and the wheels, as shown in Figure 3 and in Figure 2 also shows the RSA with details, the upper end of its cylindrical inner upper cylinder is fixed with an upper baffle. An upper mounting ring is fixed above the upper baffle. The sleeve design is fixed above the guide frame with an inverted U-shaped cross-section, and guide blocks are fixed at the upper side of both sides of the guide frame, and slots are provided at the lower side. A thrust bearing is arranged between the lower end of the upper inner cylinder and the guide frame’s upper surface. The thrust bearing is a two-way thrust bearing. The upper inner cylinder’s outer circumferential surface and the sleeve structure’s inner circumferential surface are rotationally fitted gaps. Both sides of the outer upper cylinder body correspondingly provide a long oblique slot, and flanges are provided at the lower end. The angle between the two oblique slots and the horizontal is 45°. The return spring is fixed between the upper baffle and the flange. A base provided with a shaft shoulder, a vertical slot, and a sliding way fixed vertically on both sides form a cylinder frame. The bevel gears and bevel gears in the gearbox are respectively installed on both ends of the horizontal shaft in the middle of the gearbox with overrunning clutches and mesh with the bevel gears. The bevel gears are installed on the horizontal shaft to mesh with the bevel gears and the bevel gears are mounted on the vertical shaft at the bottom of the gearbox the vertical shaft is connected with the main generator shaft and the generator the rectifier voltage regulating the circuit, and the supercapacitor form a power generation and energy storage design. A fastening bolt is arranged between the generator and the lower bottom of the gearbox. Retaining rings are provided at both ends of the horizontal shaft.

Figure 3:

The regenerative shock absorber (RSA) in the vehicle.

Transmission design

Figure 4 shows that both return spring ends are fixed between the upper baffle and the flange. The upper mounting ring and the lower mounting ring are fixed on the upper baffle at the upper end of the inner upper cylinder and the lower end of the lower cylinder for ease. Installed on the car body when the car bumps the RSA of inner cylinder and outer cylinder produce relative displacement. When pressure is applied, the spring compresses and causes the inner upper cylinder to move downwards. When the pressure is removed, the spring’s elastic force makes the upper inner cylinder moves upwards to realize the function of shock absorption. When under pressure, the return spring is compressed. The inner upper cylinder drives the sleeve structure, the thrust bears guide block, and connects the rod to move down. The guide block and connecting rod are in the long vertical slot of the slide internally sliding. The connecting rod will also slide along the inside of the oblique hole on the upper outer cylinder’s sidewall. Due to the limiting effect of the oblique slot on the fixed outer upper the cylinder’s sidewall, it slides along the inside of the oblique slot. As a result, the cylinder frame drives the vertical shaft and bevel gear to rotate clockwise. Due to the bevel gear and the bevel gear’s meshing effect, the bevel gear rotates in the clockwise direction from the right view of Figure 4 the inner ring and the overrunning clutch’s outer ring are locked in the clockwise rotation direction. The bevel gear will drive the overrunning clutch. The horizontal shaft and bevel gear rotate together in a clockwise direction. In Figure 4 the inner and outer rings of the overrunning clutch are in a non-locked state, and the bevel gear and the outer ring of the overrunning clutch are counter-clockwise. Rotate, and the inner ring of the overrunning clutch rotates clockwise with the horizontal axis.

Figure 4:

The design of the transmission mechanism that changed the two-way motion into the one-way motion.

When the pressure is removed, the return spring rebounds. The upper cylinder block drives the sleeve structure, thrust bearing, guide frame, guide block, and connecting the rod to move upward. In contrast, the guide block and the connecting rod slide inside the long vertical hole of the slide. The connecting rod will also slide along the oblique slot inside the upper outer cylinder’s sidewall. Due to the limiting effect of the oblique slot on the fixed outer upper cylinder’s sidewall, the connecting rod slides along the inside of the oblique slot. It will drive the cylinder frame, sleeve structure, guide frame, guide block composed of the slide way, and the base to rotate counter-clockwise. As a result, the cylinder frame drives the vertical shaft and the bevel gear to rotate counter-clockwise together. Due to the engagement of the bevel gear from the right view of Figure 4 the bevel gear rotates in the clockwise direction, and the overrunning clutch rotates in the clockwise direction. The ring and the outer ring are locked, so the bevel gear will drive the overrunning clutch, the horizontal shaft, and the bevel gear to rotate in a clockwise direction. Looking down from the top of Figure 4 the bevel gear drives the bevel gear, the vertical shaft, and the generator’s rotor to rotate counter-clockwise. At this time, the inner and outer rings of the overrunning clutch are in a non-locked state, and the bevel gear and the outer ring of the overrunning clutch are counter-clockwise. Rotate, and the inner ring of the overrunning clutch rotates clockwise with the horizontal axis. The connecting rod passes through the through-hole provided under the guide frame, the long vertical hole on the slide way, and the long oblique hole on the outer upper cylinder body. The shaft block is fastened at both ends. Rolling bearings can also be provided at both ends of the connecting rod. The outer side of the guide frame and the inner side of the slide way are sliding-fitting gaps. The two sides of the guide block and the long vertical holes, the connecting rod and the long vertical holes, and the long oblique holes also slump fitting gaps. A fixing plate is provided. The periphery of the fixing plate is provided with uniformly distributed circular through-holes. It is provided with an outer lower cylinder body with a flange on the upper side and a lower mounting ring at the bottom. The outer upper cylinder and the outer lower cylinder flanges are provided through the holes corresponding to the circular through the holes on the fixing plate. The bolts fasten between them. The upper end of the gearbox is fixedly connected with the lower end of the fixing plate. A thrust bearing is arranged between the lower surface of the base and the fixed plate’s upper surface. The upper end of the vertical shaft above the bevel gear passes through the vertical hole on the base’s shaft shoulder. And a pin fastens the shaft shoulder on the base.

Design and analysis

In this study, the RSA consists of the following main components, including the generator. Also, it has an outer upper cylinder with an inclined slot and flange at the outer end. Vertical long slot and long oblique slot on the outer cylinder. This article has a simple structure that converts the reciprocating vibration of the vehicle into the rotation of the generator rotor, converts mechanical energy into electrical energy, and effectively recovers the vibration energy of the RSA suspension during driving, thereby increasing the energy utilization rate.

Therefore, as a generator in this type of RSA for the current produced by the generator to become unconscious and unstable, and a rectifier circuit was designed as shown in Figure 5 the supercapacitor can be charged at high-speed and has high density and is suitable for storage.

Figure 5:

Circuit design for power storage of the generator.

The linear damping coefficient

In this part, the upper end of the cylinder was fixed, as shown in Figure 6 the upper part of the cylinder was developed with long slots inclined at an angle of 45 (x, y); converting vertical motion into rotational motion; the bidirectional rotational movement is combined with its unidirectional rotational movement, the clockwise movement of the generator through the planetary gearbox.

Figure 6:

Regenerative shock absorbers (RSAs) subjected to sinusoidal excitation.

As shown in Figure 5 the rotary damping coefficient of the generator, with parameters listed by other researchers (Zhang et al. 2016), is expressed as:

where k_e is the electromotive voltage, r is the internal resistance, and R is the external resistance.

To decide the linear damping coefficient (C_L), the proposed RSA is subjected to a displacement x, as proven in Figure 7 the input power is calculated as:

where ẋ is that the excitation, the input power includes two parts, P_L and P_E:

where P_L is the friction power loss in bevel gears and generator, whereas P_E is the generator power, which is given by:

where η_pg is the efficiency of the bevel gears, and η_g is the efficiency of the generator.

Figure 7:

Regenerative shock absorbers (RSAs) are subjected to a general input excitation.

Substituting Equation (5) from https://en.wikipedia.org/ and Equation (3) into Equation (4), we arrive at:

The rotational motion converted from linear motion from the cam in the cylinder is expressed as:

where ω_cam is the angular velocity of the cam, ẋ is the velocity, L is the load cam axial, and i is the gear ratio of the gears. Therefore, the linear damping coefficient can be expressed as:

System simulations

To investigate the performance of the planned absorbent, simulations with a curving displacement are performed to see the force and displacement circles. The proposed absorber includes the mechanical cam, slot, fore bevel gears, tapered roller clutches, two outer cylinders, and therefore the magnet Synchronous Machine. Table 2 shows the parameters of the proposed absorber.

Using Equation (14) will get the damping coefficient. With reference to Equation (15), the overall mechanical efficiency of this design consists of three components: The mechanical efficiency of the long oblique slot is used to convert reciprocating motion into rotary motion, the gears box.

To simulate the accomplishment with a curving vibration, we have a tendency to utilize the subsequent estimations: The mechanical potency of the bevel gears is η_bg = 0.97, the mechanical efficiency of the planetary gearbox is η_pg = 0.96, the mechanical efficiency of the CAM is η_cam = 0.92, and therefore the mechanical efficiency of the generator η_g = 0.91.

A comparison in the researcher (Qualifying and Report 2009), the mechanical performance of this new design is η_m = 0.77 replacing into Equation (15).

Simulations results

The RSA simulation design is established in Matlab/Simulink. The input is the motion speed of the RSA, and the output is the damping force of the shock absorber, as shown in Figure 8. The establishment of the shock absorber simulation design is mainly divided into four parts:

1. The movement speed of the RSA refers to the relative linear movement speed of the upper and lower cylinders of the RSA under external excitation. Here, the derivative of the sine wave displacement produced by the sine wave function generator is used as the input of the motion speed of the RSA.

2. The role of the transmission part is to use the oblique long slot guide mechanism to convert the two-way rotation into one-way rotation of the main generator shaft through the gear set, to collect the vibration energy generated during the driving of the car and improve energy efficiency.

3. The motor design, the brushless motor, uses the motor design that comes with Matlab/Simulink. When the motor input is the speed input, the motor output is the electromagnetic torque. Then the brushless motor model is in the power generation state, and the motor output circuit is connected to the external star symmetrical load of the shape connection.

4. The output damping force of the RSA includes linear damping force and inertial force. Among them, the electromagnetic torque output by the motor model is converted into linear damping force, which is the main part of the damping force output by the RSA and is related to the movement speed of the shock absorber. The inertial force is generated by the moment of inertia in the RSA and is related to the acceleration of the RSA.

Figure 8:

Simulink simulation model of regenerative shock absorber (RSA).

This is used to analyze the relationship between the RSA power and the input excitation and external load in the RSA characteristics. In the simulation of the indicator characteristics of the RSA, the voltage across the single-phase resistance in the external symmetrical load is measured by an oscilloscope, and the characteristics of the RSA are simulated at the same time.

Simulate the relationship between the voltage and time as showing in Figure 9 amplitude is 7.5 mm 2 Ω, and the output voltage of the RSA in different frequencies: (a) frequency 1 Hz; (b) frequency 1.5 Hz; (c) frequency 2 Hz; (d) frequency 2.5 Hz. This is used to analyze the relationship between the shock absorber power and the input excitation and external load in the shock absorber (Figure 10), Figures 11–13 talking about the relationship between the displacement loops and forces from the simulation of different frequencies at resistance of 3 Ω and an amplitude of 1, 3, and 4 mm.

Figure 9:

Output voltage of the regenerative shock absorber (RSA) in: (a) frequency 1 Hz; (b) frequency 1.5 Hz; (c) frequency 2 Hz; (d) frequency 2.5 Hz, amplitude is 7.5 mm, and resistance is 2 Ω.

Figure 10:

The relationship between force and time

Figure 11:

The relationship between displacement loops and force from the simulation of different frequencies at resistance of 3 Ω and amplitude of 1 mm.

Figure 12:

The relationship between displacement loops and force from the simulation of different frequencies at resistance of 3 Ω and amplitude of 3 mm.

Figure 13:

The relationship between displacement loops and force from the simulation of different frequencies at resistance of 3 Ω and amplitude of 4 mm.

Assuming that the instantaneous voltage across the single-phase resistor is V, then the instantaneous shock absorber power P_instant of the single-phase resistance is:

According to the paper of the previous researcher (Qualifying and Report 2009)

Then the average power P_output(ave) of the three-phase resistance of the shock absorber in a period T is:

The characteristics of the shock absorber are shown in Table 3 at frequencies of 1 Hz, 1.5 Hz, 2 Hz, 2.5 Hz, amplitude of 1 mm, resistance of 3 Ω, the corresponding shock absorber power is 2.253 W, 4.320 W, 7.055 W, 2.883 W, and in Table 3. Frequencies of 1 Hz, 1.5 Hz, 2 Hz, 2.5 Hz, amplitude of 3 mm, resistance of 3 Ω the corresponding shock absorber power is 2.581 W, 8.321 W, 8.605 W, 8.738 W, and in Table 3. Frequencies of 1 Hz, 1.5 Hz, 2 Hz, 2.5 Hz, amplitude of 4 mm, resistance of 3 Ω the corresponding shock absorber power is 8.971 W, 7.671 W, 8.268 W, 8.521 W. As the frequency increases, the power of the shock absorber also increases. The power of the shock absorber is proportional to the frequency. The results in this part of this paper were similar to the results that were found by previous researchers interested in the field of energy (Li et al. 2013b; Qualifying and Report 2009; Tan et al. 2017) (Tables 4 and 5).

Firstly start with the dynamic analysis of the basic structure of the shock absorber and analyze in detail that the oblique long slot guide mechanism converts the reciprocating linear motion into the rotation and then converts the two-way rotation into the one-way rotation of the main generator set through the gear set, thereby driving the car. The vibration energy generated in the process is collected to improve the utilization rate of energy, the transmission of force and speed in the motor, and the source of the damping force of the shock absorber is theoretically analyzed. The shock absorber is derived after certain simplified assumptions on the system. Then, the corresponding simulation model is established in simulation software. Finally, the indicator characteristics and shock absorber characteristics of the shock absorber under different input excitation and external load are simulated by MATLAB. The simulation results of indicator characteristics show that the damping force of the shock absorber is proportional to the input excitation, which meets the performance requirements of traditional shock absorbers and the damping force of the shock absorber is inversely proportional to the external load. Adjust the external load of the motor to achieve the damping force. Controllable. The simulation results of shock absorber characteristics show that the shock absorber characteristics are proportional to the input excitation. The greater the input excitation, the better the shock absorber characteristics, the higher the absorber power; the shock absorber characteristics are inversely proportional to the external load. The smaller the shock absorber characteristics, the higher the shock absorber power. The analyzed linear damping coefficient (C_L = 778.5 N, s/m), substituting into Equation (8).

Conclusions

The new type of RSA has a simple structure, it converts the linear motion to rotational motion by using the vibration generated while the vehicle is in motion. This energy rotates the generator rotor, which converts the mechanical energy into electrical energy, and efficiently recovers the vibration energy of the RSA suspension during driving, this improves the overall energy utilization rate. The performance of the RSA is to generate damping force to suppress the vibration of the vehicle’s suspension. The more uneven the road surface, the greater the damping force required to eliminate the vibration. The smoother the road surface, the smaller the damping force required. Therefore, the RSA performance indicators are generally expressed by the indicator characteristics of the RSA. The indicator characteristics of the RSA indicate the change characteristics of the damping force with the relative movement displacement during the extension and compression strokes of the RSA. At frequencies of 1 Hz, 1.5 Hz, 2 Hz, 2.5 Hz, amplitude of 1 mm, resistance of 3 Ω, the indicator characteristics can be intuitively obtained that the RSA is in tension and compression is the maximum damping force in the stroke. The main purpose of the RSA is to provide damping force and energy recovery, so the performance index of the RSA includes the energy recovery characteristic and the indicator characteristic, which is called the energy feed characteristic of the RSA. Next, based on the mathematical model established in the previous section, a simulation model of the shock absorber will be established in Matlab/Simulink, and the performance characteristics of the RSA will be simulated.