BRAKING OF A MOTOR DURING A BATTERY DISCONNECT

In one embodiment, an apparatus for motor stoppage during a battery disconnect includes a safe torque off circuit, a backup power source, and a feedback input. The backup power source is configured to supply power to the safe torque off circuit. The feedback input is configured to provide a status signal to the safe torque off circuit. The safe torque off circuit is configured to provide a switch signal to a motor circuit in response to the status signal.

BACKGROUND

A turn over event describes a situation where a vehicle or other device is tipped over. There are several safety concerns for a turn over event. These concerns may be exacerbated in electric vehicles when the electric motors continue to turn after the turn over event. In some instances, control systems may be included to control the electric motors to a stop. However, if the power source to the control system (e.g., the battery of the electric vehicle) has become disconnected during the turn over event, the control system may be unable to perform the controlled stop. The following embodiments describe apparatus and method for braking or otherwise slowing or stopping the electric motors even during a power source disconnection.

When providing the survey through a computer or mobile application, answers can be provided in real-time. What is needed is a system whereby a leader can receive the answer and respond to the employee in real-time while maintaining the anonymity of the employee.

BRIEF SUMMARY

The present disclosure may be directed, in one aspect, to an apparatus for motor stoppage during a battery disconnect, the apparatus including a safe torque off circuit; a backup power source configured to supply power to the safe torque off circuit; and a feedback input configured to provide a status signal to the safe torque off circuit; wherein the safe torque off circuit is configured to provide a switch signal to a motor circuit in response to the status signal.

In another aspect, a motor controller for a lawnmower is disclosed, the motor controller including a safe torque off circuit for motor stoppage during a battery disconnect; a backup power source configured to supply power to the safe torque off circuit; and a feedback input configured to provide feedback to the safe torque off circuit, the feedback including an indication of whether at least one blade of the lawnmower is rotating and an indication of normal operation of the motor controller; wherein the safe torque off circuit is configured to provide a switch signal to a motor circuit in response to the feedback.

In yet another aspect, a method for controlling a motor is disclosed, the method including receiving, at a safety circuit, a first feedback signal indicative of operation of a motor controller; receiving, at the safety circuit, a second feedback indicative of a rotation of a motor; and generating, at the safety circuit, a switch signal in response to the first feedback and the second feedback, wherein at least two phases of a driving circuit for the motor are connected in response to the switch signal.

DETAILED DESCRIPTION

An electric vehicle includes one or more motors that operate on battery power or other electric only sources. The term electric vehicle may be distinct from an electric car or electric automobile and encompass a wide variety of applications. Examples include lawnmowers, tillers, trimmers, tractors, utility vehicles, mobile aerial lifts, forklifts, and others. These vehicles may include control systems to provide automated motion control and safety mechanisms. In some examples, rather than an electric vehicle, the following examples are implemented by an electric handheld device (e.g., trimmer, saw).

When the vehicle is an electric lawn mower, for example, a turn over (tip over) event may result in exposure of moving blades. In the battery electric powered riding lawn care industry, it is common and required that a cutting blade be stopped in the event of a vehicle turn over. This can be accomplished many ways. For example, the system assumes that power is available to the motor controller such that the cutting blade motor can be controlled to a stop. The situation becomes more complex when the turn over event also involves the loss of power, that is, when the battery becomes disconnected.

However, during a vehicle turn over event, it may be common that power will be lost to the motor controller(s) either by the system requesting a disconnect (opening a battery contactor) or by the power source become dislodged (such is in a gravity held removable battery pack) or disconnected by the force of the event itself.

FIG.1is an example setting of a turn over event.FIG.1illustrates an example vehicle100to represent any of type of electric vehicle traveling on an example ramp101having an inclined plane at angle θ. The angle θ is measured from the horizontal plane (e.g., the surface of the earth or a line/plane perpendicular to the direction of gravity) such that higher positive numbers in degrees or radians indicate steeper angles for the ramp101. Depending on the details of the vehicle100, the path of travel, and the angle θ, situations may arise where there is a risk of a turn over event with a loss of power.

In some instances, a cutting blade continues to spin after the loss of power due to inertia or kinetic energy in the moving cutting blade. If the battery remained connected, the cutting blade motor may act as a generator, a source of power that flows to the battery, slowing the cutting blade motor. Thus, the cutting blade motor acts as a source of electrical power and the battery acts as a sink of the electrical power. But if the battery does not remain connected, there is no path for the generator source of power, and the cutting blade may spin for a longer period of time.

The following examples include apparatus that are configured to provide an auxiliary circuit to provide another sink for the source of electrical power. In some examples, the auxiliary circuit may short the phases of the cutting blade motor, causing the power source to flow through the power stage circuit connected to the cutting blade motor and then back into the cutting blade motor. More specifically, power may flow from one phase of the cutting blade motor, through the power stage circuit, and then into another phase of the cutting blade motor. The electrical power may be dissipated through the resistance of the path of the current, generating heat. The kinetic energy stored in the moving blade motor is removed by the current flow and converted into heat causing, the at least one motor and the blade to slow in response to the battery disconnect.

FIG.2illustrates an example vehicle100including wheels201, a chassis or frame202, and a seat203or other structure. A motor controller200is in communication with and controls drive motors M1and M2and also blade motor M3. The drive motors M1and M2may be connected to rear wheels201via shaft205, and the front wheels211may be mounted on castors to freely move in any direction. The rear wheels201may be independently controlled by the controller200to steer the vehicle100. Additional, different, or fewer components may be included.

FIG.3illustrates an example motor controller200. The controller200may be connected to the battery213via a fuse227. The fuse227is configured to break the connection or otherwise create an open circuit or isolation between the controller200and the battery213in the event a predetermined current (overcurrent) flows from the battery213to the controller200. The controller200may include a power supply221, a logic circuit222, a safe torque off (STO) circuit224, which may be referred to as an auxiliary logic circuit for motor control, and a power section223. The controller200provides commands, or control signals, to the blade motor M3, which turns the blade of the lawnmower. The STO circuit224, which is described in more detail below, includes at least a backup power source and a feedback from another circuit or the blade motor M3. The controller200includes may include a variety of other circuits or devices including an indicator such as a light, speaker, or display to provide information to the user. The indicator may indicate when the STO circuit224has been activated. The controller200may include an input for the user to activate (e.g., place on standby) the STO circuit224or disable the STO circuit224. Additional, different, or fewer components may be included.

The power supply221may be configured to convert the electrical signal received from the battery213to one or more converted signals as used by the logic circuit222and the power section223. The electrical signal from the battery213as well as the converted signals may be DC. Thus, the power supply221may be a DC to DC converter with one input and multiple output levels.

The battery213may provide a high voltage level to the power supply221. The power supply221may convert the high voltage level to a first low voltage level for the logic circuit222and a second low voltage level for the power section223. The high voltage level from the battery213may vary as a function of load and/or charge. The power supply221regulates or minimizes these variations in the converted electrical signals. Examples for the high voltage level include 24, 48, or 96 volts. Examples for the first low voltage level include 3.3 or 5 volts. Examples for the second low voltage level include 5, 8, or 10 volts. In addition or in the alternative, the battery213may be configured to provide power to power section223or motor circuit.

The power section223is configured to provide a drive signal to the blade motor M3. The power section223may also provide drive signal to the wheel motors M1and M2. The power section223may include a bridge or other rectification circuit. The rectification circuit may be a DC to AC converter that converts the DC signal to a sinusoidal drive signal. In the case of an AC motor for blade motor M3, the motor M3may included three phases (or four phases) and the power section223may include a corresponding rectification circuit for each phase.

The power section223receives the second low voltage level converted signal from the power supply221and turn on or off the blade motor output signal. The power section223drives high power elements or semiconductors including field effect transistors (FETs), metal-oxide semiconductor field effect transistors (MOSFETs), bipolar junction transistor (BJTs), insulated-gate bipolar transistors (IGBTs), silicon carbide (SiC) or another semiconductor switch. Any of these example semiconductor switches may include a conditioning and control circuit that receives the second low voltage level converted signal from the power supply221and activates and deactivates the semiconductor switch in response to the second low voltage level converted signal.

FIG.4illustrates an example logic circuit222for the motor controller200. The logic circuit222may include a speed control module231, a torque control module232, a motor control module233, and a trajectories module233. Additional, different, or fewer components may be included.

The speed control module231may generate a control signal for the power section223based on a target speed. The target speed may be a set value. The target speed may be received from an input device from the user. The target speed may be set by a throttle input. The target speed may be set by a speed setting. The target speed may be calculated by the motor controller200based on one or more parameters or sensed conditions. The logic circuit222may include a comparator configured to compare the target speed to a sensed speed. When the target speed is less than the sensed speed, the logic circuit222outputs a command to the power section223to increase power to the blade motor M3. When the target speed exceeds the sensed speed, the logic circuit222outputs a command to the power section to decrease power to the blade motor M3.

The torque control module232may generate a control signal for the power section223based on a target torque. The target torque may be a set value. The target torque may be received from an input device from the user. The target torque may be set by a throttle input. The target torque may be set by a torque setting. The target torque may be calculated by the motor controller200based on one or more parameters or sensed conditions. The target torque may be based on the thickness of turf or grass in contact with the blade. The torque setting may be inversely proportional to the speed sensor.

The logic circuit222may include a comparator configured to compare the target torque to a sensed torque. When the target torque is less than the sensed torque, the logic circuit222outputs a command to the power section223to increase power to the blade motor M3. When the target torque exceeds the sensed torque, the logic circuit222outputs a command to the power section to decrease power to the blade motor M3.

The motor control module233may send other commands to the blade motor M3via the power section. The motor control module233may analyze sensor data. For example, a tilt sensor may detect whether the electric vehicle is at a predetermined angle, and the motor control module233may generate and send a command to the power section223to stop the blade motor M3or otherwise slow the blade motor M3in response to the output of the tilt sensor. In another example, a height sensor may detect the height of the blade, and the motor control module233may generate and send a command to the power section223to stop the blade motor M3or otherwise slow the blade motor M3in response to the output of the height sensor.

The trajectories module233may determine velocity profiles, trajectories, or a series of speed or torque settings over time. The trajectories module233may send the series of speed or torque settings, which may be paired with time values or time intervals, to the speed control module231, the torque control module232, or the motor control module233, to control the blade motor M3via the power section223.

FIG.5illustrates an example power section223for the motor controller200. The power section223may include a phase A circuit241, a phase B circuit242, and a phase C circuit243, which are connected selectively by a switch array244. The switch array244may include at least two switches. A first switch may connect the phase A circuit241to the phase B circuit242. A second switch may connect the phase B circuit242to the phase C circuit243. In another example, other pairs of the phases of the power section223may be connected by the switch array244. The switch array244may connect the negative terminals or portions of the power section223, and the positive terminals or portions of the power section223may remain connected to the blade motor M3.

The switch array244may receive an input command or an input signal from the STO circuit224. In response to the input command or the input signal, the switch array244causes two or more phases of the power section223to be shorted together, which allows the reverse current flowing out of the motor, as discussed in more details below. Additional, different, or fewer components may be included.

FIG.6illustrates an example STO circuit224for the motor controller200. The STO circuit224may include a power source251and a logic252. The logic252is in communication with a status input device253. The logic252is in communication with a motor output254. The power source251and the battery213are independent in that failure of the battery213does not affect the operation of the power source251. Additional, different, or fewer components may be included.

The power source251is a backup power source configured to provide stored power to the STO circuit224in the event of a failure of the battery213. The power source251may include a battery (e.g., a coin battery, watch battery) and may include alkaline (manganese dioxide), lithium, or silver oxide. The power source251may include a capacitor. The capacitor may be protected by a diode or another type of reverse energy flow blocking devise. The capacitor (power source251) may be charged (e.g., continuously charged) by the battery213during normal operation of the controller200or normal operation of the vehicle. The capacitor (power source251) may be charged by the back electromotive force (EMF) from the blade motor M3and the power section223when the bladed motor M3acts as a generator. That is, when the battery is disconnected, and the blade motor M3generates an EMF voltage through the power section223to the power supply221, the EMF voltage may charge the backup power source251of the STO circuit224. When the battery213experiences a failure event, the power source251provides power to the STO circuit224. Other backup power sources may be used.

The failure of the battery213may correspond to disconnection of the battery213, for example, when one or more cables, connectors, terminals, cells, solder joints, or other components are broken or otherwise break an electrical connection with the battery213. The failure of the battery213may be detected based on the operation of a component of the controller200.

A status input253provides a feedback or status signal from the controller200to the STO circuit224. The status input253may be a communication interface, a connector, a port, a pin, or another device that facilitates the feedback or status signal as an input to the STO circuit224. The status signal indicates whether the controller200is in normal operation (i.e., whether a failure event or disconnection has occurred). There are several indicators of normal operation. The status input253may provide a power level (e.g., power pin) from a component in the logic circuit222. When the components of the logic circuit222(TTL device, AND gate, integrated circuit) have a predetermined voltage level on a power pin tied to the status input253, the STO circuit224remains in standby. When the components of the logic circuit222do not have the predetermined voltage on the power pin tied to the status input253, the STO circuit224is activated and causes the switch array244to connect two or more phases of the power section223.

Other connections for the status input253are possible. The status input253may be connected to the power section223. In this case, the feedback or status signal indicates whether one or more components (e.g., a transistor) in the power section223are operating normally. The status input253may be connected to the power supply221. In this case, the feedback or status signal indicates whether the power supply221is receiving power from the battery213. The status input253may be connected to a connector on the batter side that indicates whether or not the battery213has become disconnected.

Logic252receives the feedback or status signal and determines an output signal. In one simple example, the logic252is an inverter. When the status signal is high, the logic252generates a low output signal, and the power section223operates normally. When the status signal is low, the logic252generates a high output signal, and the power section223causes the power section223to short together two or more phases of the power section223.

The logic252may also include a combination of logic gates (OR gates, AND gates or others). The logic252may receive other inputs such as a feedback signal from a tilt sensor. When the tilt sensor indicates a tilt has occurred and the feedback signal from the controller200indicates the battery has been disconnected, the high output signal is sent to the power section223. The logic252may receive a safety signal from a safety sensor. The safety sensor may be an indication that the user is standing up or otherwise is removed from a seat, a bail lever is actuated/released, or another mechanism. When the tilt sensor indicates a safety event has occurred and the feedback signal from the controller200indicates the battery has been disconnected, the high output signal is sent to the power section223. Similar logic combinations may be based on user commands, throttle settings, temperature settings, or other devices.

The motor output254provides the output signal from the STO circuit224to the power section223. The motor output254may be a communication interface, a connector, a port, a pin, or another device that facilitates the transmission of the output signal to the power section223. The output signal may be a binary signal (low or high) or and ON/OFF signal. When the output signal goes high or ON, the power section223is configured to connect two or more phases of the power section223and the blade motor M3.

FIG.7illustrates another example STO circuit225for the motor controller200. The STO circuit224may include a power source251and a logic252. The logic252is in communication with a status input device253and sensor input device255. The logic252is in communication with a motor output254. Additional, different, or fewer components may be included.

The motor sensor input device255may be a communication interface, a connector, a port, a pin, or another device that facilitates sensor data for the blade motor M3as an input to the STO circuit224.

The sensor input device255may be coupled to a variety of types of sensors configured to measure the operation of the blade motor M3. The sensor data or status signal from the sensor input device255indicates whether the at least one motor is rotating. The status signal may include a series of pulses generated by the sensor.

The sensors may be motion sensors that detect the movement or rotation the blade motor M3or a component thereof. The motion may be mounted on, or in viewing position of, the shaft of the motor, a rotating component of the motor, the rotor of the motor, the blade, or another location. The sensor may detect movement of the rotor of the motor or a shaft of the motor. The motion sensor may be an optical sensor that detects a mark or indicia. For example, the shaft of the motor may include a mark detectable by the optical sensor on each revolution of the shaft. The sensors may include at least one magnetic sensor configured to detect windings of the motor or a magnet.

The sensors may be electrical sensors. The electrical sensors may measure the field windings of the blade motor M3. The electrical sensor may measure the back electromotive force (EMF). The detection could be considered sensorless when electrical detection is used. A detection circuit may detect the reluctance ripple in the input of the motor caused by the coil of the motor passing metal at a certain point in the rotation of the motor. The controller200may be configured to calculate speed of the motor as function of reluctance.

The STO circuit224may receive the status signal from the status input device253and the speed signal from the motor sensor input device255. The logic252may analyze the status signal and the speed signal to determine whether a battery disconnect even has occurred while the blade motor M3is still spinning. In one example, the logic252includes an AND gate261and a NOT gate262that determine whether the status signal is low or OFF (indicating that one or more components of the controller200are inactive) and the speed signal is high or ON (indicating that the blade motor M3is still spinning). In this condition, the output of the AND gate261of the logic252is high or ON and sent to the power section223.

The output of the AND gate261of the logic252causes the power section223to switch one or more power circuits by activating one or more semiconductor device to turn short or couple two or more of the power circuits together. Kinetic energy from before the battery disconnect is transferred to heat after the battery disconnect because the power sections are electrically connected. In other words, electrical energy from before the battery disconnect is transferred from a first winding of the motor to a second winding of the motor.

FIG.8illustrates an example microprocessor implementation of the example safety circuit. In some examples the controller301including processor300implements the STO circuit224. In other example, the controller301including processor300implements the motor controller200including the STO circuit224. The controller301may include a processor300, a memory352, and a communication interface353for interfacing with devices or to the internet and/or other networks346. In addition to the communication interface353, a sensor interface may be configured to receive data from the sensors described herein or data from any source for the position of the motorized vehicle100, motor M1or M2, or a wheel201. The components of the control system may communicate using bus348. The control system may be connected to a workstation or another external device (e.g., control panel) and/or a database for receiving user inputs, system characteristics, and any of the values described herein.

Optionally, the control system may include an input device355and/or a sensing circuit356in communication with any of the sensors. The sensing circuit receives sensor measurements from sensors as described above. The input device may include any of the user inputs such as buttons, touchscreen, a keyboard, a microphone for voice inputs, a camera for gesture inputs, and/or another mechanism.

Optionally, the control system may include a drive unit340for receiving and reading non-transitory computer media341having instructions342. Additional, different, or fewer components may be included. The processor300is configured to perform instructions342stored in memory352for executing the algorithms described herein. A display350may be an indicator or other screen output device. The display350may be combined with the user input device355.

FIG.9illustrates a flow chart for the apparatus ofFIG.8. The acts of the flow chart may be performed by the controller301(e.g., the motor controller200or the STO circuit224). Additional, different of fewer acts may be included.

At act S101, backup power supply is charged in a motor controller. The backup power supply may be charged by a main power supply (e.g., battery). The backup power supply may be another battery or a power storage circuit. The power storage circuit may include at least one capacitor and at least one diode to protect the at least one capacitor.

A safety circuit is powered by the backup power supply. The capacitor may discharge to provide power to the safety circuit for the operations of act S103, S105, and S107.

At act S103, the controller301(e.g., through processor300) receives, at the safety circuit, a first feedback signal indicative of operation of a motor controller. The first feedback signal indicates whether the motor controller is operating normally. In some examples, the first feedback signal may be electrically coupled to a power rail of the motor controller circuit. In some examples, the first feedback signal may be electrically coupled to a particular pin of a component of the motor controller.

At act S105, the controller301(e.g., through processor300) receives, at the safety circuit, a second feedback signal indicative of a rotation of a motor. The second feedback signal may be based on a sensor output at the motor. The second feedback signal may include pulses that represent rotations of the motor.

At act S107, the controller301(e.g., through processor300) generates, at the safety circuit, a switch signal in response to the first feedback signal and the second feedback signal. At least two phases of the driving circuit for the motor are connected in response to the switch signal.

Processor300may be a general purpose or specific purpose processor, an application specific integrated circuit (ASIC), one or more programmable logic controllers (PLCs), one or more field programmable gate arrays (FPGAs), a group of processing components, or other suitable processing components. Processor300is configured to execute computer code or instructions stored in memory352or received from other computer readable media (e.g., embedded flash memory, local hard disk storage, local ROM, network storage, a remote server, etc.). The processor300may be a single device or combinations of devices, such as associated with a network, distributed processing, or cloud computing.

Memory352may include one or more devices (e.g., memory units, memory devices, storage devices, etc.) for storing data and/or computer code for completing and/or facilitating the various processes described in the present disclosure. Memory352may include random access memory (RAM), read-only memory (ROM), hard drive storage, temporary storage, non-volatile memory, flash memory, optical memory, or any other suitable memory for storing software objects and/or computer instructions. Memory352may include database components, object code components, script components, or any other type of information structure for supporting the various activities and information structures described in the present disclosure. Memory352may be communicably connected to processor300via a processing circuit and may include computer code for executing (e.g., by processor300) one or more processes described herein. For example, memory298may include graphics, web pages, HTML files, XML files, script code, shower configuration files, or other resources for use in generating graphical user interfaces for display and/or for use in interpreting user interface inputs to make command, control, or communication decisions.

In addition to ingress ports and egress ports, the communication interface353may include any operable connection. An operable connection may be one in which signals, physical communications, and/or logical communications may be sent and/or received. An operable connection may include a physical interface, an electrical interface, and/or a data interface. The communication interface353may be connected to a network. The network may include wired networks (e.g., Ethernet), wireless networks, or combinations thereof. The wireless network may be a cellular telephone network, an 802.11, 802.16, 802.20, or WiMax network, a Bluetooth pairing of devices, or a Bluetooth mesh network. Further, the network may be a public network, such as the Internet, a private network, such as an intranet, or combinations thereof, and may utilize a variety of networking protocols now available or later developed including, but not limited to TCP/IP based networking protocols.