100 results about "Knee joint movement" patented technology

The invention discloses an intelligent orthopedic rehabilitation self-adaptive evaluation method and device based on multi-modal physiological feedback. The method comprises the steps that multi-modal physiological data including electromyographic signals, knee joint three-dimensional motion trails, plantar pressure distribution and cognitive input degree of a subject are synchronously collected; constructing a three-dimensional baseline vector according to the MMT muscle force test, knee joint ROM measurement and VAS pain score of the subject; inputting the multi-modal physiological data and the three-dimensional baseline vector into a personalized orthopedic rehabilitation model, and outputting a knee joint function index prediction value and personalized rehabilitation adjustment parameters; dynamically adjusting electrical stimulation parameters according to rehabilitation adjustment parameters output by the personalized orthopedic rehabilitation model; if the cognitive load index exceeds the early warning line, the electrical stimulation intensity is reduced; otherwise, activating the hippocampus body wave stimulation mode. Adjustment is carried out according to the real-time state of the subject, blindness and subjectivity in the rehabilitation process are avoided, and the rehabilitation efficiency and success rate are improved.

The invention relates to a humanoid robot leg structure and sole assembly based on rope driving, which comprises a hip assembly, a thigh assembly, a shank assembly and a sole assembly, the joint of the hip assembly and the thigh assembly is a hip joint, the joint of the thigh assembly and the shank assembly is a knee joint, and the joint of the shank assembly and the sole assembly is an ankle joint. A first driving source is arranged on the upper side of a hip joint and used for driving the hip to roll, a second driving source and a third driving source are arranged on the left side and the right side of the hip joint respectively and used for driving the hip to pitch and yaw, and a fourth driving source and a fifth driving source are arranged on the left side and the right side of the upper portion of a thigh assembly respectively and used for driving the hip to roll. The fourth driving source is used for driving the knee joint to move, the fifth driving source is used for driving the ankle to do pitching motion, and the sixth driving source is arranged at the joint of the shank assembly and the sole assembly and used for driving the ankle to do rolling motion. The dynamic performance of the whole robot can be improved.

The invention provides a knee joint dyskinesia function evaluation method and system. The method comprises the following steps: by collecting lower limb kinematics parameters, plantar pressure distribution data and gait rhythm parameter groups of a subject in a standard gait test, generating a knee joint motion trail map comprising sagittal plane, coronal plane and rotation trail components, dividing a dynamic phase window based on the gait rhythm parameters, calculating a fluctuation feature vector of a sagittal plane track component, performing nonlinear decomposition on a coronal plane and a rotation track component to separate an adduction and abduction motion principal component and a rotation coupling component, constructing a joint stability quantitative index, and performing dynamic space registration on a bilateral knee joint track map to obtain a joint stability quantitative index; and calculating a three-dimensional trajectory similarity weight matrix, and calculating a dynamic symmetry index in combination with the cross-side difference coefficient of the joint stability quantitative index. According to the technical scheme provided by the invention, a scientific basis is provided for personalized rehabilitation treatment.

The invention relates to the field of rehabilitation equipment, in particular to elderly knee joint rehabilitation training equipment which comprises a bottom plate, and the top of the bottom plate is rotationally connected with a knee joint amplitude adjusting mechanism; the top of the knee joint amplitude adjusting mechanism is connected with the knee joint detection mechanism, and one end of the knee joint amplitude adjusting mechanism is connected with the pressure rehabilitation mechanism; the knee joint amplitude adjusting mechanism is connected to the side wall of the bottom plate, the driving mechanism is connected to the side wall of the bottom plate, and the output end of the driving mechanism is in transmission connection with one side of the knee joint amplitude adjusting mechanism. The knee joint movement range of a patient can be accurately adjusted, it is ensured that the angle and strength in the training process meet individual requirements, and the training comfort and effect are further improved.

The invention discloses a knee joint acoustic signal analysis and inflammation detection method based on deep learning, which is based on a knee joint acoustic signal acquisition system, acquires acoustic signals generated in the motion process of a knee joint in real time, and inputs the acoustic signals into a deep learning model for analysis. Acoustic signals generated when the knee joint moves are collected; the collected knee joint acoustic signals are preprocessed through a Butterworth filter, short-time energy segmentation and Mel spectrum feature extraction method; a deep learning model based on Transformer is used for training the extracted features, a complex mode in the knee joint acoustic signal is learned, whether inflammation exists or not is judged through automatic classification, and a diagnosis result is output; real-time monitoring data is transmitted to a cloud end through wireless communication, and the health state of the knee joint is checked; according to the scheme, features are automatically extracted through deep learning, and high-accuracy recognition of the inflammation state is achieved.

The invention relates to a self-adaptive knee joint protection method and device based on motion risk prediction. The method comprises the steps that knee joint motion data, environment data and gait data of a user are collected in real time through an embedded inertial measurement unit, a pressure sensor, a myoelectricity sensor and a depth camera; the environment data comprises a ground material, a gradient and illumination intensity; the gait data comprises stride frequency, stride and gait cycle; inputting the knee joint movement data, the environment data and the gait data into a knee joint movement risk prediction model, and predicting the knee joint movement risk of the user in a future period; when the knee joint movement risk exceeds a preset threshold value, the exoskeleton is controlled through the knee joint auxiliary equipment to adjust the flexion and extension damping and the movement range of the knee joint. According to the method, the motion intention is recognized through the risk prediction model, and real-time monitoring and personalized protection of the knee joint motion risk are achieved based on the variable stiffness execution mechanism of the shape memory alloy and the gait mode.

The utility model belongs to the technical field of medical rehabilitation instruments, and particularly relates to a knee joint orthosis convenient to adjust, which comprises a knee joint orthosis body, and the knee joint orthosis body is composed of a thigh fixing plate, a shank fixing plate, a first fixing seat, a second fixing seat, a first connecting rod, a second connecting rod, a fixing disc and a rotating disc. The thigh fixing plate and the shank fixing plate are each provided with an air tap, an air bag and a fixing belt, the fixing disc is rotationally connected with the rotating disc, a limiting rod is further rotationally arranged on the fixing disc, a check block is arranged on the rotating disc, a screw hole is formed in the fixing disc, and scale marks are arranged on the fixing disc. By means of the knee joint rehabilitation training device, the knee joint movement of a patient can be limited in the early stage of rehabilitation, meanwhile, the buckling angle of the knee joint can be limited according to the rehabilitation progress, and the rehabilitation training requirement for proper buckling movement of the knee joint of the patient is met.

A thigh connecting module is connected with a first connecting rod module and a second connecting rod module through pin shafts, a shank connecting module is connected with the first connecting rod module and the second connecting rod module through pin shafts, the thigh connecting module is connected with the thigh part of an external exoskeleton device, and the shank connecting module is connected with the thigh part of the external exoskeleton device. The shank connecting module is connected with the shank part of an external exoskeleton device, and all the modules jointly form a four-connecting-rod movement mechanism so as to be attached to the movement curve of the knee joint. According to the scheme, the movement curve of the knee joint of the human body is precisely fitted through the unique four-connecting-rod movement mechanism design, stress deviation in the movement process is reduced, simple rope driving and a built-in reset spring ball mechanism are adopted, use of a complex structure is avoided, an intelligent control system or a machine learning algorithm is combined, and the movement accuracy of the knee joint of the human body is improved. Equipment parameters are automatically adjusted, so that the equipment quality and cost are reduced on the premise of greatly improving the precision and naturalness of knee joint assistance.

The invention provides a gait balance training method and system based on virtual reality, and is applied to the technical field of data processing. The method comprises the following steps: processing knee joint sequence image information of a target user to generate knee joint motion range interval information; processing the physiological parameter information of the target user in a preset time period, and generating target diagnosis interval data information of the target user; processing the gait training purpose information of the target user and the target diagnosis interval data information of the target user to generate a gait training adjustment factor; processing the knee joint activity range interval information and the clinical attribute information of the target user based on a target gait training generation model, and generating gait posture stability information and gait stability time information; and processing the gait posture stability information, the gait stability time information and the gait training adjustment factor to generate target gait training information.

The invention discloses a knee joint assisting exoskeleton, and belongs to the field of exoskeletons. The first and second inertial measurement sensors are arranged on the thigh and shank clamp mechanisms; a shell of the power assisting mechanism is fixed to the thigh clamp mechanism. A first rack and a second rack are arranged on the two sides of the shell in a sliding mode. The motor is fixedly arranged on the shell and sleeved with the first gear, the second gear and the third gear are meshed with the first gear, the fourth gear and the third gear are meshed, and the second gear and the fourth gear are meshed with the first rack and the second rack on the corresponding side. Two ends of the first and second connecting rods are respectively fixed with the lower parts of the two first and second racks; the first ends of the first and second curved beams are respectively sleeved on the first and second connecting rods; two ends of the third connecting rod are fixed with the shank clamp mechanism; the second ends of the first curved beam and the second curved beam sleeve the third connecting rod; the plantar pressure sensor is arranged on the plantar; the first inertial measurement sensor, the second inertial measurement sensor, the motor and the plantar pressure sensor are electrically connected with the development board. Accurate matching of knee joint motion characteristics and rigidity requirements can be achieved.

The invention relates to the technical field of nursing, and provides a magnetic hyperthermia nursing auxiliary system after a meniscus operation. The system comprises a multi-source information acquisition module, a motion behavior identification module, a magnetic hyperthermia parameter control module and a terminal monitoring display module. The multi-source information acquisition module is responsible for acquiring knee joint movement and regional temperature data of a patient and performing preprocessing and feature extraction on the data; the motion behavior recognition module evaluates the motion completion condition by analyzing the real-time motion trail and motion characteristics of the patient; the magnetic hyperthermia parameter control module adjusts output parameters of the magnetic hyperthermia equipment according to the identification result; and the terminal monitoring display module is used for displaying related data and providing an interaction function.

The application discloses a biped robot with a quick-change hand and a motion analysis method under special working conditions, and belongs to the field of robot technology.The biped robot comprises a trunk unit, an arm unit, a hip joint unit and a leg unit; the arm unit is provided with a mechanical hand through a quick-change structure, and the mechanical hand is divided into a clamping mechanical hand, a scissors mechanical hand and a lock twisting mechanical hand.The robot has the advantages that each movable joint of the robot is designed in a module mode, the integration and the modularization of the robot are greatly improved, a connecting rod mechanism is arranged at the rear side of a knee joint, a design of moving outward of a hinge point is adopted, the motion dead point of the knee joint is offset, the joint module can more smoothly exert force, and the complexity of the joint connecting part is reduced.

The utility model relates to exoskeleton technology, concretely is knee joint power-assisted walking device, including thigh part and shank, both are connected through knee joint, wherein the knee joint includes the hinge part I of setting in the lower extreme of thigh part, and the hinge part II of hinge connection with hinge part I, the drive module for driving knee joint is set in the upper end of thigh part, and drive module is driven the hinge part II deflection through the rope drive structure, power-assisted walking device is used for knee joint power assistance, and the hip joint needs the user to exert force alone, and the drive module for driving knee joint movement is not set in the knee joint, but moves to the upper part of thigh part, that is, the position close to the hip joint, and realizes the purpose of driving knee joint through the rope drive structure, this scheme can improve the gravity center of whole leg assembly, compared with the scheme that the existing drive module is set in the knee joint, when walking, the user, overcomes the leg assembly gravity work less, can effectively reduce the fatigue degree of hip joint.

The invention relates to a sensing technology, in particular to a knee joint multi-sensor fusion sensing method and system based on flexible fabric. The system comprises a flexible fabric sensor array, a signal acquisition module, a fusion sensing module and a classification module, a plurality of sensing units of the flexible fabric sensor array are uniformly distributed in each subarea of the front part of the knee joint; the signal acquisition module is connected to the flexible fabric sensor array and is used for acquiring a multi-channel sensing signal in real time and transmitting the multi-channel sensing signal to the fusion sensing module; the fusion sensing module extracts local time sequence features by using a convolutional neural network, and fuses global time sequence features through a bidirectional long-short-term memory network, and then the attention module weights key time steps to extract multi-dimensional features so as to realize identification of sitting posture leg lifting, standing and walking; and the classification module is connected with the fusion sensing module and is used for outputting a classification result of the knee joint movement mode. According to the invention, efficient feature extraction and adaptive dynamic fusion of multi-channel signals are realized.

The embodiment of the invention discloses wearable knee joint equipment, a knee joint rehabilitation evaluation method and computing equipment. The wearable knee joint equipment comprises a flexible substrate; the sensing unit is integrated on the flexible substrate and comprises an electromyographic sensing module used for collecting surface electromyographic signals of rectus femoris for driving the knee joint to move; the muscular tension sensing module is used for generating a muscular tension signal by detecting skin deformation caused by knee joint movement based on the piezoresistive effect; the joint angle sensing module is used for generating a knee joint motion range signal by detecting knee joint flexion and extension strain based on the piezoresistive effect; the signal processing module is connected with the sensing units and used for processing and wirelessly transmitting the surface electromyogram signals, the muscular tension signals and the knee joint movement signals to a computing device so that the computing device can determine the state evaluation result of the knee joint rehabilitation state based on the signals. The possibility is provided for remote dynamic monitoring of TKA postoperative rehabilitation, and the accuracy of rehabilitation state evaluation is improved.

The double-joint continuously variable transmission ratio structure comprises an artificial limb hip joint, a continuously variable transmission power mechanism and an artificial limb knee joint, wherein one end of the continuously variable transmission power mechanism is connected with the artificial limb hip joint, and the other end of the continuously variable transmission power mechanism is connected with the artificial limb knee joint; the continuous variable transmission power mechanism is driven by a power motor to transmit power to the prosthetic hip joint and the prosthetic knee joint at the same time, the prosthetic hip joint is driven to complete hip bending action, the prosthetic knee joint is driven to complete knee bending action, and hip and knee movement coordination is conducted through a speed adjusting motor. Under the action of a single power source, through the structure, the transmission ratio can be changed according to the hip and knee joint movement relation in the gait cycle, the hip and knee cooperation rule in the human body movement process is simulated, and therefore the movement collaboration between artificial leg joints is improved, and the energy conversion efficiency is improved.

The application discloses a hydrogel for promoting cartilage repair by piezoelectric effect, a preparation method and application thereof, wherein the hydrogel body comprises biodegradable three-dimensional piezoelectric hydrogel prepared from sodium potassium niobate, polyvinyl alcohol and polyacrylic acid. The polyvinyl alcohol is a gel state with a porous structure, the polyacrylic acid is a polyelectrolyte with a negative charge, and the sodium potassium niobate is a piezoelectric material. The piezoelectric hydrogel with the non-toxic and harmless sodium potassium niobate nanoparticles with excellent piezoelectric performance and the polyvinyl alcohol and polyacrylic acid as the main body develops a biodegradable three-dimensional piezoelectric support. The support is implanted into a knee joint cartilage defect, when the knee joint moves, the three-dimensional piezoelectric support generates an electric charge due to stress extrusion and joint self-friction, the composite piezoelectric hydrogel can generate an electric signal in response to radio stimulation to promote chondrogenic differentiation of stem cells and endogenous angiogenesis, perfect regeneration of hyaline cartilage at the cartilage defect and acceleration of recovery of the motion function.

By using the helical axis in the knee joint movement of subjects during walking, we perform gait analysis that can be used to detect early-stage osteoarthritis of the knee. [Solution] A gait analysis method comprising the steps of: calculating the helical axis of the knee joint based on motion data of the subject's lower limbs during walking; extracting the flexion phase and extension phase during the stance phase of the subject's gait cycle; and obtaining an evaluation value to assess the condition of the knee by quantifying the variability of the helical axis group in one or both of the flexion phase and the extension phase.

A method for producing a partial or total knee prosthesis suitable for human anatomy of an individual patient, the method comprising a design step of taking into account the patient's current and pre-lesion knee motion behavior, and further taking into account the patient's individual hip-knee-ankle joint (HKA) mechanical alignment, and utilizing these inputs, to produce a partial or total knee prosthesis suitable for human anatomy of the individual patient. A knee joint model as natural is recreated, where still the recreated natural knee joint model rather than the diseased knee joint model is used to create a prosthesis that recreates the natural knee joint.

The invention belongs to the technical field of motorized tools, and particularly relates to a Bowden cable power-assisted flexible lower limb multi-joint exoskeleton robot and a control method. The robot can assist the hip and knee joints of the lower limbs when a human body walks; a reversing bevel gear set, a two-way wire spool and an electromagnetic clutch are adopted, so that a single motor assists hip joint extension and knee joint bending in the left leg and the right leg of the lower limb; the prediction of the walking gait position and the gait period is realized through inertial measurement units mounted on the two sides of the left leg and the right leg; in the control system, an upper computer drives a motor through dspace to drive hip and knee joints of lower limbs to move, an inertial measurement unit performs angle feedback, and normalized gait prediction is realized. Through a designed dynamic model, PD iterative control and fuzzy PID control, the tracking of the hip and knee joint expected power-assisted curve is realized.

The application discloses a kind of based on knee joint motion mechanism's bionic joint mechanism, belong to bionic mechanical technical field.The bionic joint mechanism includes two bars four cable tensioning support units symmetrically arranged on two sides, is set in two bars four cable tensioning support unit between femur contour movement subassembly, with the femur contour movement subassembly and two bars four cable tensioning support unit cooperation setting bilateral linkage mechanism and drum wheel curved surface cooperation mechanism.The application can simulate the motion characteristics in the process of knee joint flexion by setting femur contour movement subassembly, improve the bionics and motion coordination of mechanism;By two bars four cable tensioning support unit and bilateral linkage mechanism, the mechanism has support ability and adaptability in the process of movement, ensure the consistency of two sides movement.The mechanism has the advantages of compact structure, linkage reliable, motion coordination, and can be applied to bionic robot, exoskeleton device and other related bionic mechanical system.

As shown in the "reference perspective view," this item is an exercise device with a pair of foot rests attached to the top of the main body so that they can rotate horizontally relative to the main body. For example, as shown in the "reference view showing the state of use," while seated on a chair or the like, stepping alternately with one foot placed on each foot rest and swinging the main body left and right allows for stepping exercises. Furthermore, by thrusting the feet forward alternately and rotating the main body horizontally, exercises can be performed to move the knee joints, and by rotating the feet horizontally in place, stretching exercises for the ankles and calves can be performed. This item is made of appropriate materials such as wood.

The present invention provides a knee joint prosthesis with a universal ball shaft type anti - dislocation structure, comprising: a femoral component, a tibial component, and a ball shaft connection component connecting the femoral component and the tibial component; the femoral component includes femoral condyles, the tibial component includes a tibial plateau and a tibial liner, and the femoral condyles contact the tibial liner to form an articular surface; the ball shaft connection component includes a universal ball shaft, one end of the universal ball shaft has a universal ball shaft hole, and the other end has a hemispherical universal ball, and a universal ball shaft neck is formed between the universal ball shaft hole and the hemispherical universal ball; the universal ball shaft is rotationally connected to the femoral condyles through the universal ball shaft hole. In the knee joint prosthesis of the present invention, an anti - dislocation snap ring and a universal ball shaft component with a posterior stability stop are added, which can not only meet the bionics of knee joint movement, the adaptation of mechanical properties, effectively disperse the stress of the knee joint prosthesis, but also prevent the knee joint from dislocating during movement, enhance the stability and anti - dislocation durability of the prosthesis, and further improve the service life of the prosthesis.

The present application relates to the field of rehabilitation robots, in particular to a three-joint complete gait walking device, comprising a back connecting device, a hip joint movement mechanism, a knee joint movement mechanism and an ankle joint movement mechanism; the hip joint movement mechanism comprises a hip joint mounting plate, a thigh supporting rod and a thigh adjusting block, the hip joint mounting plate is arranged on a leg fixing mechanism, and the thigh adjusting block is adjustably arranged on the thigh supporting rod; the knee joint movement mechanism comprises a knee joint mounting plate, a calf adjusting block and a calf supporting rod, the knee joint mounting plate is arranged on the thigh adjusting block, and the calf supporting rod is adjustably arranged on the calf adjusting block; the ankle joint movement mechanism is arranged at the lower end of the calf supporting rod; driving mechanisms are arranged on the hip joint mounting plate and the knee joint mounting plate. The present application is used for gait training of patients with rehabilitation needs of walking disorders, the combined movement process is closer to normal gait walking, and it is more beneficial for gait training and improves the training effect.

Disclosed is a knee joint guide apparatus which can be driven even at any point on a plane in which an instantaneous rotation center of a knee joint can be positioned by a self-alignment function, and can also implement output performance required for a walking operation through a mechanical advantage change depending on a flexion angle. The knee joint guide apparatus includes: a proximal body link provided above a knee joint; a distal body link provided at a location corresponding to the proximal body link below the knee joint; and a planar rigid body 6-bar linkage mechanism including a plurality of revolute joints and a plurality of prismatic joints, and a plurality of links between the proximal body link and the distal body link to output a mechanical advantage depending on a flexion angle of the knee joint in movement of the knee joint with a self-alignment function.

The application discloses a knee joint dynamic stability bionic protector and a control method, and belongs to the field of sports bionics. The protector comprises a high polymer composite shell, a partitioned cushion layer, a bionic multi-axis movable joint assembly and a flexible bionic ligament strip. The protector is internally provided with an angle-pressure integrated sensing module, which can collect knee joint movement and stress data in real time, and through an intelligent micro drive unit, dynamic adjustment of the partitioned damping, rigidity and support angle can be realized. The protector has high adhesion and comfort, can automatically adjust the support mode according to the user's activity state, effectively improves the dynamic stability of the knee joint, prevents injury and assists in rehabilitation. The protector is suitable for knee joint function protection in multiple scenes such as sports protection, clinical rehabilitation and daily health management.

The invention discloses a bionic joint mechanism based on a knee joint movement mechanism, and belongs to the technical field of bionic machinery. The bionic joint mechanism comprises two-rod four-cable tensioning supporting units symmetrically arranged on the two sides, a thighbone contour simulating movement assembly arranged between the two-rod four-cable tensioning supporting units, a double-side linkage mechanism and a drum wheel curved surface matching mechanism, wherein the double-side linkage mechanism and the drum wheel curved surface matching mechanism are matched with the thighbone contour simulating movement assembly and the two-rod four-cable tensioning supporting units. By arranging the thighbone contour imitating movement assembly, movement characteristics of the knee joint in the flexion and extension process can be simulated, and the bionic property and movement coordination of the mechanism are improved; and through the two-rod four-cable tensioning supporting units and the linkage mechanisms on the two sides, the mechanism has the supporting capacity and the adaptive capacity in the movement process, and the consistency of movement on the two sides is guaranteed. The mechanism has the advantages of being compact in structure, reliable in linkage and coordinated in movement, and can be applied to relevant bionic mechanical systems such as bionic robots and exoskeleton devices.

A system including a knee ranging tool: including a base configured to locate on a resected proximal face of a tibia in a knee of a patient; defining a tibial reference surface configured to run against a femoral surface of an artificial femoral component, installed on a distal face of a femur of the patient, during articulation of the knee of patient; including a set of stages interposed between the base and the tibial reference surface, configured to locate the tibial reference surface relative to the base, and compliant to medial-lateral translation, anteroposterior translation, and transverse rotation; and configured to indicate a medial-lateral translation offset, an anteroposterior translation offset, and a transverse rotation offset corresponding to a position of the tibial reference surface, relative to the base, that yields elastic deformation of ligaments in the knee over a range of motion of the knee.

The invention discloses a body-building and leg-exercising tricycle, which comprises two groups of flywheels, ratchet mechanisms are arranged in the flywheels, the two flywheels are respectively arranged on a rear wheel shaft, and transmission structures are respectively arranged on the two groups of flywheels; four sets of fixed pulleys are installed in the middle of the frame, and a set of fixed pulleys installed on the front face of a vertical stand column of the frame is sleeved with a linkage rope. The bodybuilding and leg exercising tricycle adopts rope transmission or standard bicycle chain transmission, each pedal only reciprocates on a section of arc in the driving process, the bodybuilding and leg exercising tricycle is suitable for a human body to apply force, can apply force and work by utilizing the gravity of a rider, overcomes the defects that the arm of force is zero, dead points exist and excessive idle work is applied in the running process of a traditional tricycle, and is suitable for being applied to the rider. And the riding is more labor-saving. During riding, the knee joint movement range is small, the knees are protected, and the knees are not hurt during body building and leg exercising. And due to near stepless speed change, a rider can better match the force and the speed.

1. Name of this product design: Knee-opening knee joint exercise trainer (folding model). 2. Application of this design: It is suitable for the treatment of pain and dysfunction in knee osteoarthritis, the rehabilitation treatment of postoperative functional impairment after knee joint surgery, and the rehabilitation treatment of functional impairment caused by knee joint injury. 3. The key design feature of this product is its shape. 4. The image or photograph that best illustrates the design's key points: 3D view 1. 5. The bottom surface of the product is a part that is not easily seen or cannot be seen during use, so the bottom view is omitted.