3. Joint Construction of Vector Controller and Intelligent Technology
3.1 Optimization and Implementation of Vector Controller
Automotive manufacturing has moved into a human-machine integrated production model
where automated assembly technology can save labor costs and increase accuracy. Steering
control of intelligent assisted assembly robots is an issue to be considered because
real-time adjustments in complex scenarios can increase the manufacturing floor compatibility.
Electric tools are similar to autonomous vehicles. The interior, seat, and steering
wheel must be assembled separately through direction control. The torque and tightening
directions need to be adjusted in real time. The study will improve the power tools
in the assembly chain from conventional motor power tools to remotely controlled vector
control tools to meet the needs in terms of performance tuning [20]. The general purpose of brushless DC motors is to achieve an electronic phase change
by checking the rotor position, which requires a high-position sensor to achieve the
electronic phase change of the motor. Fig. 1 shows the vector control takes the required torque value as the optimal advantage
to control electric tools and the control process.
Fig. 1. Standard DC motor vector control structure.
The conventional vector control in Fig. 1 usually uses three PWM outputs, which is difficult to implement because part of the
arithmetic link of this control requires a certain amount of program initiation and
is more demanding on the operator. Therefore, the study will use a microcontroller
and hardware circuit instead of a programming link, improving the control efficiency.
The vector control link generally involves three modes: $I_{d}=0$ control, maximum
torque control, and weak magnetic field control. In $I_{d}=0$ control, the three-phase
currents are measured by hardware; the currents are then transformed by coordinates,
and the transformation equation is expressed as Eq. (1).
After the right angle conversion of Eq. (1), the result was converted to $d-q$ using Eq. (2).
$\theta $ in Eq. (2) is the angle between the $d$ and $a$ axes. At the end of the conversion, the current
and the rotor field will be in the same coordinate system, and the motor torque equation
in this control method is expressed as Eq. (3).
where $T_{e}$ is the electromagnetic torque. $p_{n}$ is the number of pole pairs.
$\varphi _{fa}$ is the magnetic chain of the rotor. $f\mathrm{a}$ and $i_{q}$ are
the $q$ axis current. In addition, the number of pole pairs and the magnetic chain
of the rotor were fixed, so the torque is related directly to the $q$ axis current.
Calculating the current will require a calculation of the motor power, which was transferred
from the power supply, as observed with the structure. The electromagnetic power $p_{e}$
was calculated using Eq. (4).
where $u_{a}$, $u_{b}$, $u_{c}$, and $i_{a}$, $i_{b}$, $i_{c}$ are the components
of potential and current on $a$, $b$ and $c$. respectively. The torque equation can
be converted under the power calculation result combined with all kinds of equations,
as shown in Eq. (5).
$\theta _{rm}$ of Eq. (5) is the motor mechanical angle. $u_{d}$, $u_{q}$, $u_{0}$ and $i_{d}$, $i_{q}$, $i_{0}$
are the motor opposite potential component and current component on $d$ axis, $q$
axis, and 0 sequence, respectively. This control case is defined as $I_{d}=0$. Hence,
the $d$ axis component is $0$, and the two components in the torque equation can be
disregarded and simplified further as Eq. (6).
Eq. (6) can reflect the relationship of each quantity. In the case of $\theta _{rm}$ constant,
the sum of the torque $q$ axis of each component related to the component relationship
is expressed as Eq. (7).
where at constant speed and torque, the $q$ axis currents and counter potentials are
related, and constant torque control can be achieved by establishing offline calculations
and a database to apply commands to torque according to this principle. On the other
hand, the details of this control, such as coordinate conversions, require a programming
base. Hence, a microprocessor will be introduced to achieve unified control. This
optimization method will not change the overall operation logic but will improve the
control efficiency by leaving part of the process to the hardware [21]. The microcontroller used in the study integrates the FOC computing module with the
chip and implements the calculations through the engine. The hardware composition
of this controller has two motor drive circuits and two converters. The position angle
signal of the controller was achieved using a Hall position sensor. When the motor
moves, the sensor components sense different magnetic poles and transmit the generated
level to the processing components. The element speed was determined by the number
of pulses per unit time, which is a common way of sensing the engine speed. In addition,
the motor drive was implemented by the internal drive circuit of the microcontroller,
with a programmable PMD capable of motor control via voltage monitoring, achieving
interaction with the converter. The circuit element has two modules, whereas the waveform
generation circuit has functional circuits, such as pulse width modulation and conduction
control. In addition, the working status of the motor needs to be monitored through
the torque status. As mentioned above, torque control is achieved through component
current, so comparing the standard current with it can achieve the purpose of monitoring.
Therefore, modules are needed to determine the current. The circuit determination
element used in this study consists of four independent voltage comparators. The working
principle of this comparator was to compare the input signals and submit the comparison
results to the microprocessor. At this time, the three phases of the microprocessor
were used as input, and the output value after a series of arithmetic conversions
was monitored.
The signal from the microprocessor will be used as the input set for the wisdom system,
which will be transmitted through a wireless transceiver module and should have high
integration and low external possession. In the whole framework, the main assembly
realization link of the actual operation end of the operation will be done using this
motor, and the wisdom module needs to complement the other functions outside the operation
to ensure the normal environment of the assembly working conditions. The working principles
of optimized vector controllers in automotive manufacturing are divided into four
types: vector control, power-saving mode, speed control, and safety protection. Vector
control refers to motor torque control, where the vector controller can convert torque
from different directions into torque, enabling the motor to output the maximum torque.
Power saving mode refers to the vector controller automatically selecting the optimal
power saving mode based on the driving status and power demand of the vehicle to reduce
battery consumption and pollution. Speed control refers to the vector controller that
can adjust the speed and output power of the motor automatically based on the driving
status and power requirements of the vehicle to achieve the optimal driving performance.
Safety protection refers to the ability of the vector controller to automatically
select safety protection measures based on the driving status and power requirements
of the vehicle, such as overcurrent protection, undervoltage protection, and overvoltage
protection. The optimized vector controller can control the torque of the motor to
achieve energy-saving and improved power performance in the automotive manufacturing
process.
3.2 IoT-based Intelligent Control Path to Achieve
The assembly of vehicles is designed as a single component, such as the vehicle interior,
braking system, and steering system. In contrast, modern workshop assembly is usually
carried out separately. Hence, intelligent technology is needed for workshop path
planning. The study will use an automatic guided vehicle to guide the motor operation,
and the path planning will be supported inline using intelligent algorithms. A demand
analysis is needed before the path scheme. Taking the production line of a company
as an example, the analysis showed that the automatic guidance should consider at
least five production lines with nine sets of process equipment, so a 2D map modeling
is needed regarding these production elements. Based on the needs of the workshop
and the actual situation of guiding equipment in the transportation chain, the grid
method is ultimately chosen to model the workshop map and the path planning will be
based on the bionic ant colony algorithm [22]. Fig. 2 shows the mathematical model of the algorithm for the specific process.
Fig. 2. Basic process of the ant colony algorithm.
$P_{ij}^{k}$ supposes there are $m$ ants and they need to visit $n$ device points,
the distance between device points $i$ and $j$ is denoted as $d_{ij}\left(i,j=1,2,\ldots
,n\right)\,,$ the information concentration between device points $i$ and $j$ at the
moment of $t$ is denoted as $\tau _{ij}\left(t\right)$. $allow_{k}$ is the set of
ants $k$ that need to visit the city. The probability that ant $k\left(k=1,2,\ldots
,m\right)$ moves from point $i$ to point $j$ at the moment $t$ is calculated using
Eq. (8).
$\eta _{ij}$ in Eq. (1) is the expected value of transfer from the point $i$ to the point $j$, which is generally
$\eta _{ij}=1/d_{ij}$, and the importance is denoted as $\beta $. The value of $\beta
$ is proportional to the dependence of the ant path decision on the heuristic function,
when $\beta =0$, the path planning becomes a fully positive feedback algorithm. $\alpha
$ is the degree of pheromone importance and takes a value proportional to the dependence
of the ant decision on the pheromone concentration. When $\alpha =0$, the algorithm
becomes a traditional greedy algorithm. $taub_{k}$ is the tabulation of the set of
equipment points forbidden to be visited by the ants. The pheromone will be volatilized
while visiting each device point, so the volatilization factor is added to optimize
the pheromone problem in the path, and the pheromone accumulation problem is solved.
The pheromone values were updated according to Eq. (9) when the ants visited all points.
where $\rho $ is the pheromone play factor; $1-\rho $ is the pheromone residual factor;
$t$ is time. $\Delta \tau _{ij}^{k}\left(t\right)$ indicates the pheromone increment
of $k$ ants transferred from $i$ point to $j$ point in this cycle, which was calculated
by three formulae: ant perimeter, ant density, and ant volume. According to the actual
demand, this study used the ant perimeter model, and the calculation formula was Eq.
(10).
The constant $Q$ in Eq. (10) is the pheromone strength, which affects the algorithm efficiency, and $L_{k}$ indicates
the length of the path taken by the ants $k$ in the loop. Under the ant colony algorithm,
it is necessary to model the environment of empirical equipment points. The modeling
abstracts the environment into a two-dimensional space. The model then divides it
into 10${\times}$10 grids, which are divided into two categories: feasible and infeasible
regions. The mapping relationship between the established map and coordinates is expressed
as Eq. (11).
The $r$ of Eq. (11) is the area of the cell grid; $i$ is the grid number; $N_{1}$ and $N_{2}$ are the
number of horizontal and vertical grids. After the grid was established, the path
planning needed to be defined based on the requirements. In the path starting at $S$
and ending at $T$, path finding aims to find the available nodes $\pi \left(t\right)$
and satisfy $\left[0,t\right]\in X_{1}$, $\pi \left(0\right)=S$, and $\pi \left(t\right)=T$.
Path $X_{1}$ represents the feasible path and does not conflict with the infeasible
path $X_{2}$. The goal of path planning under this problem definition is to consider
the length, path avoidance, and smoothness requirements, where the path length is
calculated using Eq. (12).
$L$ of Eq. (12) represents the length; $n$ is the number of nodes in the path; $\left\| c_{i+1}-c_{i}\right\|
$ is the Euclidean distance from the point $c_{i}$ to $c_{i+1}$. The smoothness of
the path is a parameter that reflects the energy consumption of the robot under this
path and has a direct relationship with the angle between the two paths. The smoothness
of $smoothness$was calculated using Eq. (13).
where $\alpha $ is the number of turns; $\theta _{i}$ is the angle variable; the formula
was calculated using Eq. (14).
where $x_{i-1}$, $x_{i}$, $x_{i+1}$, $y_{i-1}$, $y_{i}$, and $y_{i+1}$ are the horizontal
and vertical coordinates of $i-1$, $i$ and $i+1$, respectively. $d\left(c_{i-1},c_{i}\right)$
and $d\left(c_{i},c_{i+1}\right)$ are the Euclidean distances of the three points.
Another parameter considered is path safety $safety$, which is negatively correlated
with the obstacles present in the path. The path is safer if the sum of the distance
from the path to all obstacles is greater. During the specific implementation process,
conflicts between the performance indicators may result in complex nonlinear results.
Therefore, weights will be used to assign values to each parameter, and the fitness
function $E\left(c\right)$ was calculated using Eq. (15).
$w_{1}$ and $w_{2}$ of Eq. (15) are the weights of path length and smoothness while $safety\leq 0$ suggests that
the path is feasible and participates in the calculation as a constraint. After establishing
the map model with the path planning definition, the ant colony algorithm will be
used, and the entire intelligent control link will be implemented. According to the
path algorithm and environmental requirements, the first node was calculated, and
the search for the next node was continued according to the fitness function. At this
point, the relationship between the number of ants and the initial number was determined.
If it is less than, it indicates positive operation; otherwise, search again. The
pheromone is updated when the phase is executed to determine if the number of iterations
meets the requirements. The search will be stopped If it meets the requirements. Otherwise,
the search will continue. When the path planning method automatically extracts the
nodes on the way, the points are connected using curves to reduce the sharpness. This
study used ant colony intelligence algorithms to plan production paths in complex
environments, identify the optimal path, and improve the efficiency and stability
of production lines, providing more efficient and high-quality production solutions
for automotive manufacturing.
4. Analysis of Shop Floor Operation Performance of Vector Controller Joint Intelligence
Technology
The workshop operation framework built in this study integrates vector control into
the motor to realize the assembly of each component. The SCM reduces manual programming
operations, realizes separation and interaction operations, installs the motor to
realize the assembly environment, and realizes path planning based on the ant colony
algorithm. The operation of the Internet of Things updates the environmental model
in real-time using external sensors, providing defining conditions for path planning.
Combining the two can achieve remote intelligent control and fully implement backend
operations to avoid human interference with the environment. The performance analysis
of the operation was divided into two parts: the assembly of the vehicle components,
such as seats by the motor tool; the degree of arrival of the motor-equipped robot
to the actual assembly scene. From the construction process of the vector controller,
the torque is related to the component of the A-phase current, and the conventional
vector controller is subjected to a MATLAB simulation of the current pulse and torque.
Fig. 3 presents the results.
Fig. 3. Performance test of the traditional controller.
The simulation results of Fig. 3(a) show that the vector controller is more regular and can cycle, but there is a large
perturbation in the torque output with a large up and down span. The current pulse
situation in Fig. 3(b) was similar, but the burr of the waveform was larger, causing a non-constant torque,
making it difficult to meet the requirements of fine assembly work. Hence, this paper
proposes a simulation of the micro-control scheme according to the same environment.
Fig. 4 shows the results of torque and current waveforms.
Fig. 4. Microcontrollers improve the performance of the appropriate controllers.
The microcontroller used in this study optimized the control of the motor. From the
torque waveform shown in Fig. 4(a), the output torque was more stable under the same conditions, with little fluctuation
and a small amplitude, which will help achieve specific assembly conditions. The current
waveform output in Fig. 4(b) was also more stable and smooth, and the fluctuation within each waveform was not
too large. Hence, the environment of this equipment can ensure stable output when
the current vector is controlled. The study conducted output tests under a load torque
of 1.0 N.m to determine the time required for the torque output to stabilize in a
certain environment, as shown in Fig. 5.
Fig. 5. Time required for two controllers to stabilize the output.
According to the simulation results in Fig. 5, both controllers eventually achieved the requirements, but the time to reach the
approved torque in Fig. 5(b) was less than in Fig. 5(a). Therefore, in terms of control time, the vector device optimized by the microcontroller
reached the given requirement of torque output at 0.1s, and the conventional scheme
took 0.4s. That is the output torque of the microcontroller reaches the set value
faster than that of the conventional vector control. In summary, the microcontroller
vector control scheme outperformed the conventional vector control in terms of both
the stability performance of the current pulse and the time required to reach the
approved requirements.
When the actual motor operation scheme is determined, the wisdom technology achieved
by the motor will be measured. The evaluation mainly verified the effect of the ant
colony path planning scheme constructed based on the map and provided a reference
for actual operation.
As shown in Fig. 6, path planning involves three automatic robots reaching the assembly points of the
frame, seat, and steering wheel, respectively, from the starting point. There is a
possibility of overlapping paths 2 and 3, which is a critical point to overcome in
the simulation. At this point, the assembly problem was planned based on the priority
of the superior workshop. The workshop assembly prioritized the frame, steering wheel,
and seats. Route 3 will be prioritized higher according to this requirement. Another
result of the above simulation test was a certain smoothness in the handling of obstacle
avoidance objects. In addition, the vehicles will not overlap in the conditions of
taking the priority way to go out. At this point, another set of experiments will
be conducted, as shown in Fig. 6.
Fig. 6. Path planning for three simultaneous paths.
The result of Fig. 7 in paths 2 and 3 is the case. Under the priority assignment, the automatic vehicle
of path 2 will be reached in priority if it is difficult to avoid a collision between
two paths under the working requirements in the phase direction. Therefore, in the
case of high-priority routing, it is necessary to redraw the path planning for low-priority,
and ant colony algorithm-based routing can effectively avoid rerouting. Table 1 lists the specific parameters of the above experimental path planning design.
Table 1. Path planning experiment information.
Path No.
|
Starting point coordinates
|
Endpoint coordinates
|
Path length/m
|
Route 1
|
(9.5,6.5)
|
(11.5,11.5)
|
5.845
|
(5.5,3.5)
|
(5.5,17.5)
|
14.239
|
Route 2
|
(10.5,6.5)
|
(10.5,6.5)
|
5.6540
|
(5.5,16.5)
|
(5.5,2.5)
|
14.006
|
Route 3
|
(7.5,8.5)
|
(4.5,11.5)
|
4.2259
|
(10.5,14.5)
|
(9.5,9.5)
|
4.8415
|
Fig. 7. Planning results under cross-paths.
From the information of six path planning in two sets of experiments in Table 1, obstacle avoidance path planning under a priority-constraint strategy can avoid
finding more complex detour solutions while minimizing the total length of the path,
saving workshop processing resources. Path planning will be performed with three kinds
of obstacles set up to test the obstacle avoidance function of the method in the workshop,
as shown in Fig. 8.
Fig. 8. Obstacle avoidance test of path planning scheme.
From the obstacle avoidance path planning in Fig. 8, this path planning has good obstacle avoidance performance in practice when there
are dynamic disturbances, such as worker and fixed component interference. This softens
the steering sharpness while avoiding three obstacles within the feasible area, reducing
driving energy consumption. In practice, the IoT-based sensor control will monitor
the obstacle situation in real time, and updating the path planning, in this case,
can achieve new path turnover. Performance testing was conducted to explore the planning
speed and accuracy of this method while ensuring its effective path-planning strategy.
This study used artificial path planning for comparison, as shown in Fig. 9.
Fig. 9. Performance analysis of path planning scheme.
The overall error of the ant colony algorithm path search scheme was 0.1-0.13 (Fig. 9), and the fluctuation range was not large, which was related to the obstacle setting.
The error fluctuated in a specific range of approximately 200s. Compared with manual
search, the overall error level was higher than that of the ant colony algorithm,
fluctuating between 0.1 and 0.15, with an extensive fluctuation range and unstable
performance. Planning stagnation is prone to occur if there are dynamic obstacles.
The application effect of the proposed improved swarm algorithm in dynamic environments
was examined. Performance comparison experiments were conducted using similar sparrow
search algorithms, flying mouse search algorithms, and traditional ant colony algorithms.
This experiment used the optimal path length, search success rate, and search duration
as performance comparison indicators. Table 2 lists the performance comparison results of the three algorithms.
Table 2. Three performance comparisons of the four algorithms.
Environment
|
Algorithm
|
Optimal path length
|
Search success rate
|
Search duration
|
Dynamic Environment 1
|
Improved Ant Colony Algorithm
|
24.26m
|
100%
|
6.94s
|
Sparrow search algorithm
|
25.38m
|
98%
|
10.38s
|
Flying Mouse Search Algorithm
|
25.27m
|
97%
|
11.25s
|
Traditional ant colony algorithm
|
26.68m
|
95%
|
15.86s
|
Dynamic Environment 2
|
Improved Ant Colony Algorithm
|
23.38m
|
99%
|
7.03s
|
Sparrow search algorithm
|
24.26m
|
98%
|
10.52s
|
Flying Mouse Search Algorithm
|
24.23m
|
98%
|
11.53s
|
Traditional ant colony algorithm
|
25.45m
|
96%
|
16.14s
|
Dynamic Environment 3
|
Improved Ant Colony Algorithm
|
24.49m
|
100%
|
6.85s
|
Sparrow search algorithm
|
25.57m
|
98%
|
10.66s
|
Flying Mouse Search Algorithm
|
25.38m
|
96%
|
11.68s
|
Traditional ant colony algorithm
|
26.83m
|
94%
|
16.35s
|
Table 2 lists the performance comparison results of the three algorithms. In Dynamic Environment
1, the optimal path length of the improved ant colony algorithm was 24.26m, which
was lower than the 25.38m, 25.27m, and 26.68m for the sparrow search algorithm, flying
mouse search algorithm, and the traditional ant colony algorithm, respectively. Moreover,
its search time was 6.94s, which was less than that the 10.38s, 11.25s, and 15.86s
of the sparrow search algorithm, the flying mouse search algorithm, and the traditional
ant colony algorithm, respectively. In dynamic environment 2, the optimal path length
of the improved ant colony algorithm was 23.38m, which was lower than the 24.26m,
24.23m, and 25.45m of the sparrow search algorithm, the flying mouse search algorithm,
and traditional ant colony algorithm, respectively. The search success rate was 99%,
higher than the 98%, 98%, and 96% of the sparrow search algorithm, the flying mouse
search algorithm, and the traditional ant colony algorithm, respectively. In Dynamic
Environment 3, the optimal path length of the improved ant colony algorithm was 24.49m,
which was lower than the 25.57m, 25.38m, and 26.83m of the sparrow search algorithm,
the flying mouse search algorithm, and the traditional ant colony algorithm, respectively.
The search time was 6.85s, which was lower than the 10.66s, 11.68s, and 16.35s of
the sparrow search algorithm, the flying mouse search algorithm, and the traditional
ant colony algorithm, respectively. These above results suggest that in the three
dynamic environments, the optimization performance of the improved ant colony algorithm
was better than that of the comparative algorithm. Therefore, applying it to workshop
path optimization can improve the workshop work efficiency. Finally, a specific processing
and production workshop was studied, and the combination of the motor and automatic
path robot was tested. The operating environment and parameters were set and put into
use. Assembly experiments were conducted on the steering wheel, seat, and frame, and
the assembly was successful, as shown in Fig. 10.
Fig. 10. Combination of Vector Motor and Automatic Robot for Automobile Assembly.
Fig. 10 presents the experimental test of the assembly realized by the automatic path equipped
with a vector motor, which is the actual test of putting the above two automatic operations
into use. The assembly scores of all three components were above 60 points. The highest
score appeared in the assembly experiment of the frame and seat. Hence, the intelligent
technology of the joint vector controller constructed in this study can at least meet
the installation requirements of the frame and seat.